If I understand your question correctly, your house is under contract, earnest money has been deposited and buyer has 30 days to complete the transaction.....will you get the earnest money if buyer "backs out" because he cannot get the house financed?
No. I do not believe based on your question that you would be due the earnest money deposit.
Most contracts are subject to buyers obtaining financing, if so negotiated. So, this buyer would not be "backing out" on the deal.
The lender must approve the loan, and then, if a buyer changes his or her mind after being approved for the loan it would make this very different outcome. You could possibly retain the earnest money....I do hope you have a Realtor that has protected your interest in the contract and is staying in touch with this buyers lender as well....if the buyers lender does not communicate ...Keep showing the house and try to get a "back up" contract.
Hope this helps.