Can runners advance if batter strikes out and ball gets away and hits backstop?

From team Rep. Choy manager:

There was an incident in our game last week. Runners on first and second and 1 out. The batter struck out on a pitch that the catcher missed and hit the back stop. Our runners were not allowed to advance. I questioned Mel Wise and he said the runners should have been allowed to advance. He will inform his umpires about this. If you have any other similar incidents, please report them to Mel Wise for resolution in future games.