Can't purchase the Suntouched Special reserve until you have the quest.  I tried to buy it before getting it, and it wasn't on the vendor :(

Where the vender go?

Where the hell is the vendor for the reserve? This quest is pissing me off!

Not the Inn by the entrance to Silvermoon, the Inn at the Royal Exchange (area where Auction house and Bank are located).  See the map for "Vinemaster Suntouched".  This Inn is to the left as you come into Royal Exchange from south, entrance a few steps down from 'road level'.

Standing right next to the inkeeper, enter the city, turn right, follow the path to the next large open area (you'll hit another one of the small stair rooms) and go left downstairs. Enter the building and he's to the left.

Can only buy during quest.

My Quest Helper told me to go to some place south of UC lol