I am not in Cocoa and I don't know your specific contract terms, but from your previous question, it seems to me you have kept all your contract terms and the lender ended up accepting another offer ahead of yours.
They (realtor, bank, nor title company) should not be able to keep your cashier's check. BTW, the money should have been turned over to the escrow company if you have opened escrow. If your agent did what he/she is supposed to do, the escrow company should have that check and should be sending that back.
However, the money should not have gone to escrow unless you have a formal acceptance from the bank. But from your other question, the bank did not accept your offer but another person's.
So, if I understand everything correctly, the money should come back to you.