I’m pretty sure I just bought the Celestial Armor and it didn’t (permanently) take my gems. I don’t want to spend the gems doing testing (even though I shouldn’t have them…), but I think I may have closed out the app or lost wifi for a sec shortly after purchase. Figured I’d give a heads up just in case there’s an issue with buying armors.
I’m on an iPhone 6S, OS 9.2.1. STUDS account name. Please don’t take my gems! 
