If they were inactive their default world would be the same as yours. That being said I think they are still in the process of updating lodestone and such. I was still on Cornelia up until 5mins ago it said Durandal.

Dunno about forced transfers. But like a few people they might have messed up the transfer process and they ended up on another world. Or maybe was forced.. who knows but I dont think theres a way to turn back regardless