As I list bank owned homes, and have worked with buyers on buying them too, I can say that most of the banks behave in similar fashion with respect to your question.
The standard CAR puchase contract has a default 3 day time to respond to an offer. This number can be changed to something else. It sounds like you have specifed a 30 day closing, but I am assuming the time to respond to the offer is still at the default 3 days. So at 5pm on the third day after you wrote the offer, the offer has offiicially expired.
In practise, this date often slips, and banks will usually do their counter offer "verbally" anyways. So negotiations are happening, but the contractual dates have long sinced passed. After "verbal" acceptance, it may take a week before the bank will sign your purchase contract and you can officially open escrow and get the clock ticking on any contractual time periods. As a listing agent or a buyer's agent, I am not happy with the process, but I guess we have to learn to live with it. In a court of law, I'm sure a buyer could challenge many of the policies and procedures banks are using in both REOs and short sales.
The only way to know the status of your offer on the property is to have your realtor speak with the listing agent. Make sure that another offer has not been accepted and that you are still in the running. Then make a decision if you want to stay in the running. Banks are notorious for not looking at expiration dates on offers and responding long after the offer has expired. If you do not want to continue with that transaction, you should formally withdraw your offer.
The one truism with offers on short sales and REOs is, he who has the most patience and perseverance usually wins.
Wishing you all the best in finding your perfect home at a great price and Dare to Dream.
Real Estate Consultant
RE/MAX Pals Verdes Realty
Without an expiration date, it is still open until you rescind your offer.