Seems he said he doesn't know what. Is it possible to find out from the "someone" what it was they put in there? This is weird sounding. Sounds like someone did whatever they did, acrimoniously / maliciously. If it was a metal part, there are magnets on retractable extensions. Maybe see if one could fit down in there and pick it up. Good luck.
2016 Honda Rebel 250 - The "Piglet."
AFR sensor equipped and downsized to a 0.105" main jet.
The only changes so far.
Bought on 6/29/19 with 44 miles.