No. But if they don't have a riser stem in stock that's about the same value as the one that come sont he bike, it's not entirely unreasonable for you to pay the difference.

Consider also that most people swap stems on stock bikes to higher/shorter ones rather than longer, and many shops end up with bins of unused OEM 120mm stems.

That said, the guy sounds like a nitwit and should have tried to work with you on getting the fit right on the bike you wanted.