Nothing is permanent in bitcoin, and a transaction that's not accepted or propagated by miners and 'lost in limbo' is, with increasing probability, headed toward the opposite of permanent.

Getting the move of funds to go through should be as simple as backing up the wallet, importing it into another (more proper) wallet app and sending a new transaction with a fee attached. Or maybe deleting the cache of the iOS wallet app could work, but I have no idea how iOS or any of their apps work, so be sure to have a backup anyway.