Screw fell in dash mist vent

Ok, so I was resting some screws on my dash, and managed to butter finger one of them down the demisting vent holes, since changing to a 70 dura rear motor mount, this guy is causing teeth jarring rattles during 1-1.5k revs during acceleration. I've looked for vent pathing diagrams to get an idea where it is sitting but no luck, I've tried a magnet on a wire and can't really tell if I'm even close to where it could be.

Any advice?
2014 Mazda3 S GT auto, 2008 MX5 6-speed
You may want to stop by a dealership parts department and ask if the counter person can show you the relevant assembly diagrams.
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