Episodes where you think the person disappeared on their own accord...
I think Maura Murray ran away, overwhelmed by everything that was going on in her life and it seems the show didn't report certain things like how much pressure her family put on her to be the best, and she didn't seem to live up to those expectations.
Lee Cutler ran away, unhappy with his home life. But what happened since is still a mystery.
Bradyn Fuska seemed to be running from a theft.
John Glasgow may have run away, afraid that he could face serious jail time.
Ray Gricar I can't help but think ran away because he was in some sort of trouble. The ruined laptop and a search about how to ruin a hard drive seems strange.
Joey Offutt I think met someone online and ran away after murdering her infant son. She could have met with foul play or committed suicide sometime later.
Charlie Allen Jr. also suffered from a mental disorder and someone had seen him after he disappeared.
Brian Barton seemed to disappear on his own and by suicide, but there has never been a body. Steven Koecher also points towards suicide.
Brandy Hall may have run away because her life became very troubled due to her husbands involvement with growing marijuana.
Jeremy Burt could have run away, but foul play also seems possible especially when the burned car showed up.
Jeremy Alex and Toni Lee Sharpless also had mental disorders and seemed to run away on their own.