What kind of buyer submits an offer under the assumption that the home WON'T appraise? What if it does APPRAISE? Well this is exactly what happened.
Are you saying the buyers backed out even though the house appraised? If the appraisal contingency and other contingencies were met then legally you may be able to sue to force them to close.
What is your Realtor's take on this? I would definitely say the buyer's realtor is out of line. Of course he owes it to his customer to advise him in the best way possible. That includes giving his opinion of the value of the home, but he owes it to his customer also to explain what happens when it does appraise at the asking price. I'd recommend you have your Realtor rattle the other Realtor's cage - complain to him, complain to his broker, and threaten to take it up with the local or state Realtor board. The only thing a Realtor has is his/her reputation and you'd be surprised how they sometimes change their tune.
Now at the end of the day, a Realtor can't force their customer to do something they don't want, but they can make them aware of the potential consequences of their actions.
That sucks Shirley because it sounds like they weren't really moving forward in good faith on this transaction. Lean on your Realtor for advice on this and maybe you should speak to an attorney. I hope things work out!