I had planned to do this post about Rusty Staub about a month or 2 ago but Night Owl Cards beat me to the punch. The basic mystery that surrounds Staub is that he did not appear in the 1972 or 1973 Topps sets. That was unusual for a player of his stature.
Now they only thing that I can recall why that may have happened had to do with his 1971 Topps card. I thought that I read somewhere that Rusty did not like his Expo nickname of "Le Grand Orange". Well if you look at the back of his 1971, it mentions this nickname. Wa la - he disappeared from Topps cards for 2 years. That is my only guess why that happened.
One other baseball card mystery that surrounds Staub is that he never once appeared on the Kelloggs sets that came out between 1970-1983. The only other star that I can recall that never appeared on those sets was Hank Aaron. Aaron did appear on a 1991 Kelloggs set.