No, checkme.txt is never deleted; it gets overwritten each time the script starts, though, so the scenario you described never occurs.

The thing's been working great, too -- almost too well! It was pretty hilarious the first couple of times I tried to restart the script because I'd made a change to the code. It just kept popping back up again! It was like playing whack-a-mole. I've since concluded that stopping the checker first and then stopping the script is the preferred technique!