Most of us have done similar things. A recent example was at MCACN. I had my black RS/Z shipped and in the Sinister 69 display. I had to move my car, and two other cars to several locations during move in. When the actual display location was available couldn't locate my key although I was sure I put them on the drivers floor. Without the keys I couldn't move the car or have it transported back to FL. I'm pretty busy with Vintage Certification and thought perhaps they fell inside one of the cars I was inspecting. I checked my car at least 6 times and even contacted a friend who is a locksmith.
I checked a 7th time and found when I got out of the car quickly i pushed the rubber mat way forward along with the key. The transporters paper mat was what all I checked under. Once I removed the paper I saw the rubber mat and the key up under the pedals. I was relieved but pissed at my stupidity of rushing and not being careful. Lesson learned I think