Frame Size Question??

[KnottedYet]

No, the 15" as it was in the shop wouldn't fix your reach discomfort, because the bars would still be lower than your body wants them. The only way the 15" would feel right to your body is if they put on a taller stem, sort of like bringing the bars up to the same relative (and comfortable) height as they were on the 17". What might feel different on the smaller frame/taller stem is that you'd have the bar height and weight distribution your body likes without having to lock your elbows to reach it, and without feeling like you want to slide the saddle forward. Did the shop measure your upper arm to torso angle on both bikes? Torso to horizontal? Did they do the plumb-line from your knee to the pedal spindle when they set up your saddle?

Pictures would really be good.

Is your seat post really only 1/2 inch out of the seat tube?

Edit to add: If you love the bike, don't worry about the size. Ride lots, get strong, feel the bike love. But a couple months down the road, if you still feel like you can't bend your elbows and you still feel like you want to slide the saddle forward, ask your shop for some help. There are lots of ways to tweak fit.