This literally just happened ...
I left my desk for a few minutes. I checked my mailbox, recycled a soft drink can, and visited the bathroom. All told, I was probably gone ten minutes, tops. Up until that time, I'd been at my desk for a couple of hours.
When I returned to my desk, I found a chat window from my boss. "Are you at your desk. (Name) has been trying to get a hold of you. Please call him ASAP."
There was NOTHING indicating that (Name) had been trying to reach me. No chats, no e-mails, no voicemails, nothing. I'm probably being overly sensitive, but this really bugs me.