This is my first breeding season and from what I understand ovulation is pretty hard to miss (but I'm sure I'm going to miss it).
As for how you know if they've bred and you don't see, there is no sure fire way to tell that I know of. If you keep them on paper you might some times see marks on the paper after they've locked. You just want to keep track of who you paired with who and when you paired them. I've only seen one lock from my male spotnose so far, but he doesn't lock for long so it's possible I missed the others.