Saints Row 2 hacker?

I just bought Saints Row 2 (I know I'm late) and during gameplay a message popped up saying that somebody wanted to join my game. But this somebody's gamertag was a bunch of numbers like 554987165849891742474. I denied it because I didn't understand what that was. Later on somebody else wanted to join my game and it looked like a regular gamertag. What was with the numbers gamertag? Was that a hacker or something? He/She/It tried joining my game a few times but I denied it every time. I looked all over the net and couldn't find anything on this so I decided to post this here. Has anyone else ever experienced this?

or someone who just made a gamertag with a bunch of numbers.

or he could also have just made a free account on his xbox rather than pay for another month of gold, and just put random stuff down.