Unfortunately the only way you can be positive is to purchase new remotes. Erase the memory as you did before and then program your new remotes. I would remove the batteries from the old remote and discard it just to prevent problems in the future.

rangrfn and neither will the one you have in your hand. You have erased the memory of the receiver. But when you program the remote how do you know the remote that was stolen doesn't have the same code? You don't!

I know for a fact that the one that was stolen will not work when you program the ones that you have.
Because when you erase the memory all remotes become inoperative. Trust me I do it all the time.

rangrfn you are pretty sure of yourself and you don't even know what model this poster has. Sometimes "knowing for a fact" is a lack of experience.

Don, I have been installing openers for over 10 years, so I am pretty sure that I know what I am doing. And that is a fact.

Hi mtnmansgirl, the odds are VERY low that an erased powerhead would still work with a stolen remot ethat is not realigned.

Use the lock button if youhave one when you go to bed or out of town.

The odds of a home invasion or burglary via a wondow ar much higher than the 1 in a million (sometimes billion with some models) type odds the old remote will still work.

Or , if you have a lock button on your wall control, lock out remotes, and buy and use two keypads as your remotes.