I hate when this happens. It happened frequently with a (former) friend, who would leave her purchases, doggie bags, cigarettes, etc. etc. She would always call my house after I made the drive all the way home (never on my cell) and expect me to drive all the way back (10 miles) to get them back to her. I put a stop to it after the umpteenth time, by asking her before she got out of my car, "Are you sure you have everything?" and do a run through of everywhere we went that day. If she still forgot something, it would have to wait until the next time I was in her direction.
I think it might be a control issue, at least in her case. (BTW, this is the friend I mentioned in the "are you late if everyone else arrives early" thread.)