From a technical point of view, I'm pretty sure there's no difference between a screenshot and having the QR code in your wallet. The scanner just scans the pattern itself, just like a normal barcode, and there's no way for it to know/register whether the code is shown via a picture or a wallet. If it didn't work, the problem is something else, like the screenshot being of bad quality or something like that.
For what it's worth, we were 10 at the game and 9 of us had our own QR codes that were sent to us via sceenshot.
