In the packet of documents that I was given to use I was told I could not take a "security deposit" until the day of property transfer when I could do the walk-through with the renter. Instead I was to use a "Holding fee Agreement" and then apply those funds to the first months rent. My advisor (CPA and experienced landlord) included a clause in the Holding Fee Agreement that it would be refunded if the tenants failed to pass a screening or credit check. On move in day the tenants will have to supply me with a cashiers check for the security deposit, pet deposit and last months rent. These funds have to then be held in a separate account (I cannot use them!) until the lease is terminated.
The others are right, you have signed legal documents with definitive obligations on both parties so check the wording of the document carefully and compare it to the rules listed in the NW Justice Project. Morally, it sounds like you have a case but perhaps not legally? Owner should do the right thing and give money back tomorrow, but legally they may have 14 days to return it. You need it now to get another rental and attorneys are expensive.
Your situation really struck me yesterday due to my own personal experience at the time. I'm not advocating that you NOT hold these people accountable but I am saying you need to be practical about it.