Any updates on this bug? I hate having open quests that I can't complete. I have the issue of not finding him anywhere after trying to send him back to the Gn. I wish I could just abandon it all together.

"Buddy" is not essential and can die on trip if not escorted, which might be why people have lost him.

For more infos about that side quest, take a look here:

It is annoying, but the quest marker specifically states to escort buddy back to good neighbor. He runs into raiders, and 2 different groups of super mutants. He will most definitely die, or get "taken" if he isn't escorted.

You gotta escort and kill everyone. Even better if you can anticipate so Drinking Buddy can keep walking.

And don't leave him walking to Goodneighbour alone because it will be bugged again. He wouldn't get in the hotel and your mission stuck.