I thought I saw Santa on Midnight?

That sounds really weird. Sorry I can't tell you exactly what it was. If you really believe it was Santa then maybe it was. Or maybe it was Fairy Niff (when I was little my mum always told me that Fairy Niff is the one that watches you all year and tells Santa if you were or nice). I don't think you should do anything because it may not have been anything but if it happens again try to think about what is going on at the time.