Thank you for all the information on a similar situation when giving up custody of one's child to their spouse and hopefully it worked out well for all in your family.My opinion only:
I have a sibling with a history of addiction problems who gave up custody of their toddler to the other parent and agreed to a no-contact order until the child turned 18. The other parent changed the child's name, moved just a couple of counties (less than an hour) away, and later had the child legally adopted by their spouse. Even with the child's new name and a rough idea of where they lived, it took years after they turned 18 for me (their aunt) to find them and let them know that their biological family wanted to know them. Since the child wasn't a missing person and my family had no legal standing to access any information about them, we couldn't just go to the court house and obtain their information, and we didn't want to hire a PI (or anything similar to that) because it felt overly invasive.
It may be a big assumption, but I'm guessing this man's family was in a similar situation, but with the added challenge of the fact that he really didn't have an online presence or attend school. I'm not surprised they were unable to find him, especially if they weren't sure if he wanted to be found.
IMO:
What I don't understand about this case and looking for the victim after he hit 18 is that HT knew who her mom's ex-husband/victims father was and he lived just a few miles away and said she's been looking for the victim for a decade.
She even knew that the father Sullivan had died in the beginning of 2023.
The victim's father was alive when the victim hit 18
Not being insensitive to Tessman but that is a lot of valuable information to start with when looking for someone.
On the flip side even if she had found the address of her mother's ex-husband and knocked on the door looking for the victim there's no guarantee any info would have been provided to her by either Sullivan on the victim's whereabouts.
Looks like all that's left is knocking on neighbors doors asking if anyone has seen the son/step-son?
Private investigator and they cost $$$.
It's such a tragic and sad situation for HT and her mom and family too and hopefully the force is on their side and the victim will one day want a reunion and go from there.