You should have been advised that your money was at risk until a full commitment from Wells Fargo - including satisfactory appraisal was received.
You may have recourse against whomever advised you to pay the money up front - but unless you have something in writing - no recourse against the seller.
With an FHA loan - the case number - and appraisal will stay with the property address. If you are in an primarily FHA market - it may be advisable for the seller to reduce the price to appraised value. See if this is a possibility.
Unless they DO consider working this out with you - they will face the same problem with any other FHA offer that comes in.
If they don't do it, complain to the real estate managing broker and even file a complaint with the local board of REALTORS.
Then, once you get your deposit back, find a new real estate and mortgage broker.