[cheebacheeba]

I speak only of my personal views on the matter...they may, or may not turn out to be accurate, I am just providing to you what some people will not.

His mother knows, but she's not going to tell you.
He's a spineless fuck that didn't have the balls to front up about being unhappy, for one reason or another, in your relationship. He may have even been cheating on you.
I'd say that within a week, you'll either hear from him again, crawling back without so much as a good excuse (eg - doesn't want to tell you he had another prospect in the first place, let alone that he was fool enough to follow up on something that wasn't a sure thing, and it backfired on him...) it may not even be another female...however, if this is the case, and he DOES come back to you, I would advise against blindly taking him back, your judgement on this matter will set you up in terms of how you will be treated, and the kind of treatment you will ACCEPT in the future.
OR... you won't hear back from him at all.
If it's the latter, No doubt at some point you WILL find out where he is, and through questioning the RIGHT people - eg - NOT someone who will adamantly defend this person and their actions out of a feeling of family obligation...not a person that will lie, perhaps even an ex girlfriend, or an enemy.
Perhaps a little subtle strategic surveillance of hangout areas, friends and family, workplaces...etc would also be advantageous.

My apologies for being so blunt, but I think that aside from a minute possibility that he's "lost", or actually suffering some kind of emotional problem he didn't want to confront others with (although, I personally think these things should be discussed with yout partner out of RESPECT), one of the abovementioned scenarios is in fact the case.

Of course there is the possibility that he's either been injured some place out of town, or he's dead...neither of which you can do a great deal about.

Sincerely - BJA