The 3 Different Mints

Certainly - I know that I got my 2009(P) Presidency cent in early December 2009, something like three weeks after release, after my uncle went to Moscow with that coin in his pocket. Surely many other such cents would have ended up in San Francisco instead (New York to San Francisco is probably a much more common travel destination than New York to Moscow, especially in winter).

EDIT: The only reason we even know about any wrong-mintmark coins is pretty much when no such coins of the other mint were made in that year (this is the case with the 1922 no D, and kind of the case with the assorted no S proofs because there were no proofs of that date made in Philadelphia).
The other possibility could be them turning up in official mint sets and rolls, I suppose - that's how we know about the mints of Godless dollars; but certainly there were no official San Francisco mint circulation cent rolls (that's kind of the point).