Jason,
In my opinion, I think that refund is your money. You have already closed the deal, the mortgage company got their part and should be on to the next loan. Whenever one of my borrowers gets a refund (insurance, title insurance, MIP, escrow, etc.) I let them know that is their money. I just got paid from the loan closing and anything 'extra' that gets paid to you, should be yours to keep. Is the mortgage company or anyone else saying that you owe them more money? If so, tell them to go pound sand. Your business with them is done once you sign the docs and the loan gets funded.