My wife didn't let me forget this one for a couple of years
This was before smartphones were popular in the U.S. - this was just a regular cell phone. I was working at a client site, installing new racks and filling the racks with new servers and other equipment. When I was done, I cleaned up the work area, throwing away the packing material. I left the client site and headed to the train station. I went to call my wife to let her know I was on my way home - whoops, no phone! I realized that I had thrown it away with the packing material. I went back to the client site to look for it, but no joy. My wife was NOT a happy camper. Lucky for me her sister works for one of the major mobile phone companies. My sister-in-law got the phone replaced quickly and inexpensively. I now have a healthy neurosis about my phone!