Thank you! Loving the game so far otherwise!
Edit: ok so I guess I was in the middle of the nuclear option quest and when he reappeared to help me finish the quest, he was on his back o the ground "following" me in a glitchy way by sliding on the ground. I wasn't able to get him back up but I did send him to a settlement so I can at least pick up different people now. Hopefully when he slides his way back to the settlement he will stand up at some point.
Update: I sent him to red rocket, but he has not shown up yet after hours of playing. Luckily I can pick another companion.
Advice: just don't bring a companion through the nuclear option quest.