What would you do with an off-hand remark from a 7 year-old about his friend being abused?

This evening I heard my youngest son say to his big brother “Joey’s mom kicks his butt all the time.” He said it in a very off-had way just in the course of conversation. When I asked what he was talking about he back-peddled telling me he didn’t say anything. When I asked if Joey is being hit a lot by his mom he got really quiet and shook his head. The kid has been to our house for play-dates and I’ve never noticed anything out of the ordinary about him, but of course I was never looking either. What would you make of this comment?