I always use one USB flash disk on my MacBook Air (OS X 10.10.3), but I lost it recently. I need a way to view when the last date & time the USB device was connected to the computer.
Unfortunately peripheral connections are simply something that isn't logged by your Mac. Just think - why would it need to keep a written log of when a USB drive is plugged in?
Hope you end up finding it again!
Apple's USB Prober should do the trick