Yes, all cars reappear in the Used Car Dealership, however, some cars reappear on a regular basis, other cars reappear rarely, but if you keep checking eventualy it will come back.
But, the really rare cars can sometimes take maybe 3-4 weeks of actual real time game playing before this happens, but I have seen the R92 in there many times so it probably won't be aslong as that.
Just keep checking after every 3-5 races and it'll pop up sooner or later.
Maybe you could put an advert up in the GT5 marketplace and make a trade??
I've seen a few available for trade.
