Someone had left the thrust washer out of mine at the last tire change before I purchased it..... needed new wheel, new flange, new final splines.
My story too. First time I took the back wheel off, found everything destroyed.
I had the same concern about measuring and replacing the thrust washer. Last time I pulled the back wheel and measured the thrust washer, I compared it to a new one right out of the package. The old one was thicker by.005". I just reused the old one. Evidently new ones can vary in thickness.