An update and a thank you
Turns out I may not have needed to worry as much as I did about Little Dude fitting back in with his siblings.
I got him up to the barn in the carrier and set him on the floor till I could figure out exactly where to put him. His siblings came running right over and started investigating. He was standing up on the crate door trying to get out. So I opened the door.
This is the result:
I closed them into their pen for a bit and went to refill the feeders on the bees.
I came back to this:

So I think he's going to be just fine.
The thank you is for the number of you who reached out last night and this morning. I've learned that in most cases when a litter is orphaned, none of the piglets survive. Of the 7 who came to the NICU, 6 are still alive.
It's probably a good thing that I didn't know the odds and just focused on keeping them alive.
Though I will say this is probably the most social litter we have ever raised and anyone who has had our pigs before knows they're social anyway. These guys are just a touch above that (and kind of demanding when it comes to head scratches)!