Oh, I definitely wouldn't count on it. I'm just pointing out that it does happen. It would of course be easier if you had physical tickets or a print out because they'd be even less likely to ask for ID. That's why I don't mind paying the extra fee, if there is one, when I buy tickets way in advance.
If it was just through Telecharge or Ticketmaster I'd definitely just call and ask to see what they say. Good luck!