Heading back to the airport after a week's trip Stateside, I stopped off at a mall for some last minute shopping. Popped in the bathroom at a department store, and put my phone down, thinking to myself that I mustn't forget it. I think you can see where this is going...
Dropped the rental car off, and walking to the terminal, went to check the boarding pass on my phone... Ran back to the car, and couldn't find it anywhere. So, I had to grab a taxi back to the shopping mall, where thankfully, the phone was exactly where I'd left it. Tipped the driver well, as he'd saved my arse. Thankfully I made the flight still, but was doubly annoyed with myself not just for leaving the phone, but for not checking while I still had the car...