I am not sure why all the angst about the subject being a short sale ...is it because the subject sale price is lower than your non short sale comps?
Assuming you are not following the advice of this MAI, of course you can value the subject higher than it's contract price. You do have one REO comp, perhaps that price might be weighted the most, and explained why.
Though there might not have been advisory opinions for just commercial (according to your statement,) the Appraisal Foundation, Fannie, Freddie, as well as many court cases of res and commercial have opined that both short sale and REO sales can be used as comps, and need to be considered if their presence indicates market trends...even if you don't use them as comps in a report, an appraiser should at least disclose the short sale/REO sale and listing activity and discuss the impact in area.
If your appraised value is above the sales contract price, so be it. Just explain why.