I can't remember the last silver coin I found in circulation or in the reject tray of a Coinstar machine. I still check, every time I go to the store but it's the usual Caribbean, Mexican or Canadian fare, or just off-spec US coins.
Abby used to be my partner in crime as her little fingers could sweep up the stuff from the reject tray in the blink of an eye, along with those coins jammed under the slide cover. Sadly no more, so now it's down to me.
I've picked up $100s worth of coins since retiring in 2011. I get lots and lots of quarters from the local car wash during the morning walk with the pupster. People stack them on top of the coin slot ready to start feeding them in once it starts beeping and just drive off and forget about them when they're done. (you can't get coins out of your pocket with wet hands!) After the car wash we cut through the parking lot of our local store before returning home via the beautiful Pinellas Trail, a repurposed CSX branch line for hikers and cyclists. The parking lot is always littered with coins, usually cents but sometimes I've found banknotes too. It's very rare that we return empty handed.
I reckon it must be at least a couple of years since my last silver coin though. So I was very pleased to find a silver Cuban 10 cent coin struck in 1952 to mark the 50th anniversary of the Republic. It was sitting in the reject tray of the Coinstar machine at our local Publix along with two worn and presumably underweight nickels from the 50s.

It's nothing very valuable, I just added it to my swaplist for $3.50, but there's something very satisfying about free coins, even more so when they're silver.