wandering mind

I was driving home from work last night, stuck in pretty heavy traffic. There was a bright yellow pickup truck in front of me. At some point, as were creeping along, my mind began wandering. Some time later, I realized that while I was keeping up with traffic and all was well, I had no idea where the bright yellow truck was.

How do you lose a bright yellow truck? No exits near by...It unnerved me a bit, just kinda of losing that truck that had been right in front of me and not realizing it.