May have just found the answer on this site!
http://www.toyota-4runner.org/4th-gen-t4rs/143424-replaced-cvs-now-have-steering-knuckle-seal-issues.html
From member King in 2013:
"recently did the same thing and had the same problem as you. it took some research and visiting all the auto parts...
Spindle Bearing Dust Seal
Not sure if a fluke failure or bad design but I know a lot topics and people buying hub bearing assemblies from various people online to do replacements.
I just replaced driver side this weekend on 2011 4Runner 4WD. Has about 110K. Wasn't too bad except separating hub...
