What prevents miners in a pool from retaining the reward? From what I understand miners submit their hashes to the pool. What prevents a miner to disengage the pool as soon as she finds the right hash?
The payout address for the miners mined blocks is the pool's moderator address. If the miners are working on blocks with a different payout address (ex. their own), the pool moderator can tell and act accordingly by either banning them or simply ignoring their work.