This is heartbreaking news but unfortunately not all that uncommon. We have had similar experiences at our sanctuary, or even been informed later that the bunny died due to carelessness. The solution is to please not breed any more rabbits as there is already a problem with overpopulation, abandonment and neglect. Every one of our bunnies is a personal friend and when something like this happens we are astounded that there are so many heartless, careless people who have no business owning any animal.

I do sympathize and hope that you get Smokey back.
I agree that you should probably go door to door in an effort to locate him. You might offer to refund the fee as a "reward" for returning him. The other thing I thought of is that you might look around the neighborhood to see if Dad turned the bunny loose and that might be why you aren't hearing from them. You are doing the right thing and I do hope it all works out for you Heather. Bunnies are too precious to lose in this manner.
Good luck and my prayers are with you.