ASA Men's C Div. Live Ball Question

[HonoUmp]

I have been an ASA Umpire for more than 20 years and in all my time of playing and umpiring, I have never seen what happened in a game I called over Labor Day weekend. ASA Rules, live ball with stealing allowed. Runner on second base, pitcher throws a pitch which was a strike. (ball still live). Catcher returns ball to pitcher and overthrows pitcher. Instead of running, the runner on second base steps off his base and picks up the ball and throws it back to the pitcher. OK, what is the call? Just a dead ball when touched? Or is the runner out for coming off his base and touching a live ball? Or something else? I don't know the answer and cannot find it addressed at all in the ASA rules book. Help please.