Cat, can you post a photo of this "fuel filter nut" which has to be removed in order to do an oil change?
Are you talking about the disc with hex nut, with spring and thimble-like screen behind it?
These things get stuck on all kinds of scooters. If gets chewed up, whole kit is less than $10 on ebay.
Most of us never find anything in the screen after a while....so, you could just leave it on there.
I might not know what you're looking at....
A DT300 owner will know.
Stig