Sunday morning I walked out to the 997 and realized it was unlocked. I would dismiss this as me simply being absentminded when I returned home last Saturday night. However, this seems to happen every so often and I know I have locked the car when I left. Has anyone noticed anything similar?

Mine is a 2009 997 S

 

If you put the key in your pocket and move wrong it can hit the unlock button.

 

If you hit the unlock button and don't actually open the door, it re locks it for you.
I wish it did that for the frunk.
The possibility increases that, yes, the OP has lost it.

 

With the key in my pocket and walking around the garage my car locks and unlocks, when buttons are pressed inadvertently. But Garygoose997 is correct that if it unlocks and you do not open any doors, it will re-lock after a few seconds by itself.

 

I feel your pain, I have done this a few times. I wish there was a beep when the door was locked or unlocked.

 

Your post implies the OP ever really had it to lose. j/k

The key is ultra sensitive, so that might be the issue. Suggest you make a habit of, when walking away from the car, lock it and watch the lights flash twice ... then you know it's locked up tight.

 

My alarm goes off for no reason from time to time, if that makes you feel any better . . .

 

It would be nice for the key fob to have "lock" and "unlock" buttons, like most cars, instead of a single button.

 

On the 997.2 cars, can't speak to the 997.1, the car only flashes the light when it is locked. If something is not properly secured the horn will sound. I thought I read somewhere that this could be change through PIWIS.

If the system works the way it should even if you don't remember if you hit the button and hit it again the car should lock after the timeout period.

 

It is just anxious to be driven again! When the battery is starting to get low on juice, the electrical gremlins seemingly take over. I would check your battery/charging system.