This has definitely happened to me... and frequently! For me personally I think it's linked to my bp as I've never gotten an ADD diagnosis. But that's just my best guess for me personally.

The wandering around forgetting what you were going to get is something I do literally all the time. I write myself a lot of notes or I'll repeat something in my head over and over until I've gotten what I needed. It really wasn't a big deal until I started losing the plot midway through a conversation. Then it just got plain embarrassing.

Believe it or not... I played memory games for a while and it helped out immensely at the time.