I have gone to the new kind of site. The lamp on the right bottom of your message is to tell admin that you have a new idea!
I deleted some of my past private messages, including one of yours ( I didn't suppose this would affect the original!).
I also noticed that I tried to read a message sent to me as part of the feed of the day,when I tried to read it here, it said "Oops this message no longer exists" I put this in the little lamp on the right. Admin replied that either the message was inappropriate in their taste and they had removed it, or the originator had deleted it!
What happens when you check in your name (green band) and your "my activity"? Does it show your past messages?
Try and tell me! Computers have ways that is not of our own!!!