"There are plenty of straws. How about Starfleet confiscating my trans-warp equation, and now some madman's using it to hop around the galaxy?!"
Scotty's the guy who identified the device in the wreckage of Khan's jumpship. I'm sure if someone else found it and realized what it was, there could have been something of an outcry. But he brought it right to Kirk who brought it straight to Marcus.