[JanS]

Congrats!
Do you have any snails in the tank? If so, that may be where the eggs are going.

 

[JanS]

That's great news that the 3 original eggs are still there.

Actually, I've found more batches hatch out without my knowledge, than the ones I keep an eye on and try to do what you're supposed to.
I think as long as you have good cover (like lots of mosses), they find plenty to eat, and seem to avoid being eaten.....