As Zimbo says, the magnet will always show some "filings" to a greater or lesser degree, but the ring fragments are not normal. Have you kept them? Could you photograph them against a ruler so we can size them up? Can you work out the approximate diameter from these pieces? It could help to determine where they've come from.
I've been looking in the parts manual, and there are quite a few shims and, what they call, "snap rings" (number 7) in the gear box - I wonder if it could be one of those.
In view of what you've found already, Mr Gazza's advice to check the gauze filter is definitely worth taking. You'll need a 14mm allen socket and you'll also have to remove the exhaust link pipe. It's a hassle but, in the circumstances, worth the effort. When replacing it, tighten the filter itself and the plug to 42Nm. Make sure too that the washer goes back the right way round.
If you have kept the fragments, try showing them to your friendly Ducati mechanic - he might be able to identify the part from the remains.
Good luck and keep us informed!