Ok, I pulled the distributor. Those pieces are definitely from the wear plate. There appears to be a shim between the wear plate and the gear, so I am even more lost.
There is some wear from the thing spinning, which appears to have forced the whole shaft upwards, which in turn started to melt the cap and rotor. I always thought that the camshaft would pull the shaft down, but that doesn't seem to be the case.
My previously complemented wear pattern on my distributor gear doesn't look so good either.
I have no idea what went wrong here.