Next time you mount a tire, make sure you line up the tire badge with the valve hole. That way, next time you flat, and the cause is not obvious, you can find the puncture in the tube, and line it up with the matching spot on the tire, and then see if there's a tiny wire or piece of glass or whatever. This has helped me several times.

You'll know if you're pinch flatting, because the puncture is always a snake-bite pattern of two holes where the tube was pinched.