I totally forgot about Ethan, I think that was his name. He was with Tara when they got attacked by the sand walkers on the bridge. He would be someone that Rick would be amused to see. Ethan may have found and brought these people to help attack Negan. I remember Ethan having some issues and wanted to go on a 30 day run with Tara to gather his thoughts.
I agree that the group wasn’t from the Kingdom because of the next week’s clip shown during the Talking Dead. It showed the main fighter from the Kingdom still there. So they have to be completely Newbies, too many men to be the Amazons. Now we have Alexandrians, Kingdom people, a few Hilltoppers, Newbies and possibly the Amazons to join up to fight Negan. Maybe.
I think the character that went missing was Heath - young-ish black dude with Buddy Holly glasses and mini-dreadlocks.