The pitching was in jest but I've never seen an umpire bend down and clean plate with a brush without at least putting hand up first. It takes a second to do this and then point to pitcher which puts it in play. Everyone assumes there is time when the umpire is cleaning the plate.
I have seen a player steal home in college this year when the pitcher and catcher were talking and the umpire was not looking. The umpire had to admit he did not call timeout but that it was assumed which is not true. He made the runner go back which was wrong and fits directly into your situation.