I wouldn't say anything about it right now, but just wait until you next speak to H. Then mention that next time you'd really apprecite it if he let you know if he was planning to take S somewhere as otherwise you'd worry where he was.
And leave it at that. I know it's not acceptable for H to do this, but I'm not sure it will help you to call H on it strongly. What would be a 180 for you in this situation?
