Very unlikely is an understatement...very^999999 unlikely more like it. Most USB drives have caps anyways that protect the plug. Those that don't probably have a grounded metal shield around the connectors. I have an A-Data MyFlash that doesn't have the metal part of the plug (just a flat stick with the 4 pins on the side) but it came with a little sleeve to put it in to prevent damage). As long as the data pins are covered (which all should be), there's barely any risk. Even if they're exposed, there's still very little risk.