I just pulled this out of my rear differential. How screwed am I?

apatter8

A little background info:

Two weeks ago I took my car to Road Atlanta for my first ever track day. Everything went great, until my last session of the day. Halfway through, I smelled a foul odor and was immediately black flagged along with the Viper in front of me. They checked out both cars briefly, parked the Viper and sent me back out. I still smelled the odor for the remainder of my session (2-3) laps.

Afterward, one of the track officials came over and said that although they parked the Viper, he now was pretty sure the issue was with my car. Said I probably just scorched the rear differential fluid, and I should change it out at my first chance. I drove my car home just fine.

So my car sat parked for the last two weeks while I waited on my redline oil and gaskets. Well today I finally got around to draining my fluid, and after draining I found this lodged in the drain port:



Whatever it is, it's magnetic. What broke?