basket interference

[Ralph Stubenthal]

I have a question about BI. In a summer league game the other day, a player on a fast break went in for a layup. His teammate followed closely behind. He shot the layup and it started rolling on the rim. His teammate (the one in hot pursuit) jumped and tried to slam the ball in while it was on the rim. I called the basket interference. But the ball did not go in but instead it bounced off the back of the rim and flew toward mid court. I had already blown my whistle and called BI and gave the ball to the other team at the baseline. My question is: is it offensive basket interference if the ball does not go in? Or, should I have blown the whistle only if it had gone in or if had been done by the defense and not gone in?