Sorry to hear that man.

If your opener isn't changing the code each time it sends a signal to open, that could be the vulnerability (older and cheap openers don't do a good job with this). One foolproof way to keep the opener from opening is to put it into vacation mode, it won't accept a signal from anything, the only thing that will open it is hitting the switch manually or entering the security code (on key pad types). However, this defeats the purpose of having an auto opener if it won't open when you pull up to drive your car in. Since I don't park my cars in the garage it doesn't matter so I leave it in vacation mode all the time.