Taurus 2003, started car, forgot house keys, went inside to get keys, when I came back out, the doors were locked, what would cause this?

I am wondering if this is, or should be a recall. First time this has ever
happened. I often have to go back  inside for items I forget after I have started
the vehicle. However, this a.m. when I came out, the car was locked, & had to
call my roadside assist to come help, as I did not have a second set (lost
them...tells you how many x's I forget stuff & have to go back). Is this a recall
problem, or what?  I checked the recall notice & it is not on there, has anyone
else had this problem with being locked out???