I guess I would say your options are:
1. Taking it to a luthier who guarantees their work - problem solved (probably the most expensive route)
2. If all of the wood grain lines up and it fits together perfectly, try some glue (I see Titebond mentioned quite often on the luthier groups I joined, some swear by HHG (Hot Hid Glue) but it seems like a PITA to use, since it has to be at exactly 145 degrees for application among other things. You could also try regular wood glue, if ithe break lines up really good.
3. You could use epoxy instead of glue.
4. You could try a dowel/glue rig. The key here is that the holes have to line up perfectly. I don't think I'd try this option.
5. Buy a new neck and bolt it on. You'd have to do some research to find a neck that fit. Then you'd have to install it and make sure the angles are right.
If it were me, I'd probably call the luthier first and see how much it would be to fix it. If that's more than I would want to pay, I'd also ask him how much it would be if I tried to glue it myself and then took it in...as sometimes they'll charge more for fixing bad repairs (glue would be the easiest to clean up, though). Then I'd try to glue it just because it may work, and glue is cheap. Epoxy may work better, but it would be harder to clean up. With gluing or epoxy, you need to make sure it's clamped firmly in place and then know what the dry time is - and double that (IMO, just to be safe).
Also, medical disclaimer - I am not a luthier, just some guy who likes to build/fix stuff.