Well, now I'm not so sure. As I get older, there is a lot that falls into the I'm not so sure category...

I haven't had this symptom since I posted this message, and I drive the car every other day. But what I failed to mention is that the shift lever release sticks when it hasn't been used (car hasn't been driven) for some time. When I remove my fingers, it sometimes doesn't return all the way to its normal position (flush with the bottom of the shift lever). When this happens, I can't remove the key. On the events in question, I didn't try to remove the key because I got out to close the garage door. I am wondering if this is what happened, and since the car was on a slope, it was more prone to roll.

I left the car for a winter once, when that lever first acted up. I looked into trying to remove and lubricate it 5 years ago, but forgot about it because it started working better and was a PITA to get off.