Dropped third strike interference?

[John Robertson]

This play actually happened in a game I umpired in 1983. It recently came up in a discussion, and I was asked to make this posting to see if other umpires agree with my ruling. Here's what happened:

Two strikes on the batter. The next pitch bounces in front of the plate. The batter swings and misses for strike three. The pitch eludes the catcher and hits the backstop. (At this diamond the backstop is only about 10 feet behind home plate.) The ball ricochets hard off the backstop and rolls along the first base line. Both the catcher and first baseman see the ball and move in to field it. The batter-runner has no idea where the ball is, but he starts to run to first base. The ball ends up between the batter runner's feet--who accidentally kicks the ball into the bench area along first base!

After due consideration I called the batter-runner out for interference because, even though it was totally unintentional, he took a play away from the defensive team.

Would anyone out there make a different call?