Over the years few things have fallen off my bike, all due to my negligence. The latest are my riding glasses today that I hung on the handlebar then forgot to pick up. It fell off and was quickly crushed under car tires. Years ago one of my bags fell off because I did not re fasten it after taking something out. Somebody actually picked it up caught with me. I had not realized what had actually happened. The most dangerous thing you can do is try to retrieve whatever fell off. Not worth it.