Some states (like mine) don't yet have a law requiring a scrap dealer to even identify someone who brings in a quantity of any kind of metal, although some will get vehicle information (or more) if they're suspicious of somebody. A guy in a nearby county got busted for stealing aluminum light poles, even though he took the pieces (and they were just that) to a dealer in another area. The dealer accepted the stuff, but wrote down his plate number. Tie plates aren't as easy to cut up into unrecognizable chunks as copper cable or aluminum poles are, but we've had people stealing quantities of all three materials from rail yards in this area.
Then again, if a company recently upgraded a line, had a bunch of old plates that were too small for the new rail, and didn't want to haul all
of it to the scrapper, they might have some left over to give to Dave.
I used to know where there were a couple of them left laying around, not on RR property. Shipping 'em from here to Oregon might not be all that cost-effective, though.