The contract is a very important part of any business deal, especially construction and real estate. From what I've seen above, the only legally binding document you have is a receipt? Even if it is at the bottom, in small print, I doubt that the real estate company would be obligated to return any of the money. The only thing you probably have on your side now is the good faith of the realtor.
Hoever, if you can prove that the house wasn't taken off the market then that would violate any written or verbal agreement that was made.
What company is this that you're dealing with anyway?