I'm sorry you had to experience that

Even so, don't be discouraged from keeping these guys. Everyone makes mistakes at the start, I certainly did.

I think Michael is right about lowering the water, it should prevent your other little guy from getting out. As for how he got out, check the corners of the lids. If you don't press them down enough sometimes, there's large holes that a frog could get out of. I know, because I've seen my Chorus frog, Chrome, squeeze through one with ease.

And I know exactly how you feel about being terrified of taking the lid off of a tank and putting it back on. I'm always terrified when that I put the crickets in my Chorus frogs' tank that my little rascals are going to leap out and hop away too fast to catch them!