I suppose some pools accepts the transaction, and sends it backwards. Otherwise it would be stuck forever in limbo.
This is not hiw bitcoin works. A pool cannot "send it back". There is nowhere to send it to, and they don't have the private key.
The pool either confirms it, or they don't confirm it. There is no way for them to "accept it and send it back"
So then please explain how it was sent back? I honestly don't know lol.