Overview of MISSING: Melissa Casillas
This Crime Junkie episode examines the disappearance of Melissa Casillas, a Los Alamos National Laboratory employee who vanished on June 26, 2025 after last being seen on surveillance video walking alone near Highway 518 in Taos, New Mexico. The case quickly split Melissa’s loved ones into two camps: one believes she walked away on her own, while her relatives on the Mondragon side believe she was the victim of foul play. The episode focuses on the conflicting family narratives, confusing evidence, and the unanswered questions surrounding Melissa’s digital footprint, finances, and movements that day.
What Happened on June 26, 2025
The last known timeline
- Melissa drove her husband, Mark Casillas, to work at Los Alamos that morning.
- She returned home around 7:30–7:45 a.m. after realizing she had forgotten her security badge.
- Around 1:00 p.m., she visited her daughter Sierra at work and brought her lunch.
- She was later captured on video at 2:18 p.m. walking alone along Highway 518, carrying a small backpack.
- After that, she disappeared.
What was left behind
When Sierra and Mark returned home, they found:
- Melissa’s work badge
- Her keys
- Her purse and wallet
- Both of her cell phones
- Her reading glasses, sunglasses, toothbrush
- A 90-day supply of thyroid medication
Her phones were especially alarming: both had been factory reset, and her iCloud backup had been wiped.
Key Evidence and Odd Details
The house and vehicle
- Melissa’s car was still at the home.
- There were no obvious signs of a struggle.
- Mark noticed unfamiliar tire tracks in the driveway.
- Investigators later found fresh mud on Mark’s hunting boots and a small stain near a fish tank that tested positive for blood in a presumptive test.
The digital trail
- Melissa texted and emailed in ways that suggested she may have been creating cover stories for the day.
- Her phones were reset at different times:
- Older phone: 8:02 a.m.
- Newer phone: 1:38 p.m.
- Investigators could not recover her iCloud backup.
- The episode suggests she may have intentionally erased data, though why remains unclear.
Financial stress
- Melissa and Mark were in serious financial trouble:
- Overdrawn accounts
- Garnished wages
- Maxed-out cards
- Security clearances suspended
- Numerous lawsuits/claims over the years
- Mark says Melissa had recently applied for a personal loan for Sierra’s beauty school tuition and was rejected shortly before she vanished.
Family Conflict and Competing Theories
The Casillas side
Mark and his daughters believe Melissa:
- Left voluntarily
- Was overwhelmed by financial and personal stress
- May have been trying to start over
Mark also floated multiple possibilities over time, including:
- She left with another man
- She moved to another state
- She may have been helped by someone connected to a job opportunity
The Mondragon side
Melissa’s parents, siblings, niece Jasmine, and other relatives believe:
- She would never abandon Sierra
- Mark may know more than he’s admitting
- Her disappearance could involve abuse or foul play
They pointed to:
- Mark’s behavior after she vanished
- His changing explanations
- Alleged financial control and emotional abuse
- His quick shift toward theories that she left on her own
Important Leads and Why They Didn’t Settle the Case
Lloyd’s highway sighting
A longtime family friend, Lloyd, said he saw Melissa near Highway 518, appearing to stumble beside an older blue Dodge truck.
- Mark initially dismissed the sighting as not being Melissa
- Police reportedly accepted that dismissal and did not immediately follow up
- Later, after Mark visited Lloyd, a surveillance video surfaced showing Melissa walking alone on that same road
The Rick Valerio tip
A tourist reported a bizarre encounter with a man on horseback who claimed he had found a decapitated body in the mountains.
- The man was identified as Rick Valerio
- He drove a blue Dodge truck
- Police later interviewed him and appear to have discounted him quickly
- The episode raises concerns about whether the lead was explored thoroughly enough
The Diego Martinez angle
Melissa’s family initially suspected Diego Martinez, Sierra’s ex-boyfriend, because:
- He had a violent history
- He had allegedly threatened Melissa
- He had sent Melissa sexually explicit texts But the case does not appear to have developed far on that theory.
Bigger Questions the Episode Leaves Open
Did Melissa leave voluntarily?
Evidence that supports this theory:
- She was seen alive on camera walking alone
- She appears to have reset her phones herself
- She told different people different stories to free up the day
- Her finances were in crisis
Or did something happen after she left?
Questions that keep the foul-play theory alive:
- Why wipe both phones and her iCloud?
- Why would she leave behind everything else, including medication?
- Why was she walking on Highway 518?
- Why did Mark keep changing his theories?
- Why did investigators move so slowly on some leads?
The most unsettling possibility
The episode also raises, but does not settle, the possibility that Melissa:
- Left to start a new life
- Left under pressure from someone else
- Or may have taken her own life, though that theory is not strongly supported by family or police
Unresolved Status
As of the episode:
- Melissa remains missing and endangered
- Police have not officially ruled out foul play
- There is no confirmed suspect
- There has been no bank activity, passport use, ID change, or prescription refill
- Investigators continue to lack a clear explanation for what happened after she was seen on Highway 518
How to Help
If you have information about Melissa Casillas, New Mexico State Police are asking for tips.
- Tip line: 505-425-6771
- Reward available for information leading to answers
The episode ends with the central plea being simple: someone knows what happened to Melissa, and her family wants the truth—whether that means she walked away or someone made sure she never came back.