THE one way I could see it ending ok is if he had some other clothes either with him personally or with the person he may have or may not have been meeting (since it doesn't even seem completely conclusive he was meeting anyone, but possibly just getting a drink)
If he'd wanted to just leave/walk away, ditching (or changing out of) the very recognizable outfit he had on would make it VERY easy for him to leave the concert and have no one one realize it on the cameras (or even eyewitnesses) since they'd have been looking for the wrong clothes.
And if they really had talked to any people he may or may not have been meeting, if he just up and walked away from his life, if they only had been asked if they knew his whereabouts or when they last saw him, they could possibly be able to honestly say they didn't know where he was and that they last saw him leaving the area...because if he left alone, they may truly not know.
Though obviously that'd mean no one would have copped to carrying clothes for him to change into (and some might say they "just" didn't "offer" that piece of information up) as it seems unlikely something LE would have asked outright, some may think that wasn't being dishonest. (NOT that I agree with it, but I have no doubt some would rationalize that way)
Heck, if something bad happened to him or he was 'taken' against his will (not sure I see how that could at all be possible) I suppose someone could have forced him into other clothes and accomplished the same thing - him not being seen leaving as no one would be looking for other clothing. Again, I think that's unlikely b/c it was way too crowded for that to seem even remotely feasible, but...I guess it's another option. Just not another likely 'happy ending' possibility like the above.
