I've had pretty good luck retrieving the things I've left on the bus. I think the only think that didn't turn up at lost-and-found was a baseball cap. The other stuff I've left behind, most notably my Kindle and my phone (on separate occasions), I was able to pick up at Metro headquarters the next day, or in the case of the phone, later that same day.
On another occasion, I managed to get off the bus with my phone, only to have it slip out of my pocket through a previous undetected hole. A young woman named Katie found it lying in the grass where I'd disembarked, and started calling people from my recent calls list to try to track me down. A clever strategy, though if she'd looked at the contacts she would have seen the very first entry was my own email address, with which she could have contacted me directly. But calling my brother and sister worked too; they emailed me and told me to call my phone so Katie and I could talk about returning my phone. Unfortunately, the ringer was turned off for some reason, so she missed the call and the texts I'd sent. Eventually we did get in touch somehow and I got my phone back.
The moral of the story, I guess, is check your pockets for holes. Or maybe it's make sure your ringer is turned on. Regardless, I haven't lost my phone since, so whatever the lesson is, I seem to have learned it.