Looks like you should have laid some money on it the first time you saw it, then they can't sell it out from under you. However, if you did have money on it, then you should have a receipt with the rifles serial number on. If you do indeed have a receipt with the serial number, you can insist on them getting your rifle back.
Since it's been years since I bought my Featherweight, what is the going price for a new one now? It shouldn't be much more than $600 and I'm sure there are plenty of them around..