If they don't get back to you before the opening the next day, assume you are not filled, unless there is some incredible market-wide dislocation.
If you end up with a fill later and lose money, file an arbitration claim. It's one sure way to get their attention, and if you win, they may have to pay punitives in addition to actual damages and the costs of the arbitration. Remember, you are a customer and the broker has a duty to exercise reasonable care.
Contrary to popular belief, the arbitrators generally side with the customer when he has a reasonable case.At least, that's what BD's tell me. My dad is a part-time arbitrator for NASD. He seems to think customers get a really good break if they have a case.
However, if you file, you'll probably never get to arbitration as a
loss for the broker becomes discoverable public info. He'll settle.