How short is too short?

I walked to the cafeteria at work to get a hot chocolate. Stopped to peek at the newspaper. Was reminded of something I should do, or look up or something.

By the time I got back to my desk, I couldn't remember what I'd intended to look up.

It's about 15 seconds from cafeteria to my desk.

I don't think I've had a traumatic brain injury recently, but I might have forgotten that as well.