But the client wouldn't care, it would see the reorg and notice the transactions were back to being unconfirmed and would broadcast them again. Presuming no double spending occurred then the transactions would be relayed and then included in blocks. So rejoining is not a problem, as long as there were no dishonest who spent on the island and also spent those same coins on the main net as well.
Is there no time limit for the how long after a transaction is created that it would be rebroadcast? What happens if a transaction is based on another one that has not been rebroadcast?