It looks like my first comment was pretty close to what I found. (evaporated)
There's nothing but tiny particles in the grease and the boot. No large chunks.
Assuming there was a bushing in there to begin with, whatever the material was has disintegrated on the r.h. end, no evidence of a bushing having ever been in the l.h. end. My previous rack had nylon bushings in both ends, and they broke apart in larger pieces. Whatever material this one was ,it appears the grease/
oil dissolved it.