Don't need to check? But what if.....

Everyday I try not to check as do all of those with OCD. We tell ourselves over and again that we should not and sometimes manage not to. But what if? I know the words "what if" are very dangerous and destructive to those with OCD and we should not entertain them but what if someone leaves the back door unlocked? You usually try not to check it as 99 times out if 100 they remember to lock it. This morning I was about to leave for work and I noticed that the key was not in the cupboard next to my vitamins so I looked at the lock and there it was. I wondered if he'd turned the key highly suspecting he had not. I pulled the handle and it opened. I was annoyed because of the security risk but also because he knows I have OCD and that this will not help. So now I am left thinking does this mean I do have to check everything?! My rational mind says not but my OCD is giving me an evil grin. I wonder if I can put this down to one of those occasional things and continue to walk away from the doubt each time I get the urge to check. What do you think?