If any of you are on LinkedIn you will see that it accesses your details and matches you with people who know the people you know.
The reason I asked the question before last (before it was mentioned is was 'only' people who had cleared their boxes, which now seems not to be true) is, these links can happen accidentally in software and so if you, for example, deleted a thread or had a post deleted, it could have read the name and although not deleted all posts on the thread, may have a link to your name on a PM and got rid of that person on there through a dubious link.
Or some corruption/hacking going on. Hopefully tech/security are on to it but they'll need to run tests so may take a little while.
Many years ago there was an awful breach when 'someone' had accessed individuals contact lists and forwarded their private emails to everyone on their contact list. I received a personal email that someone on my contact list had sent to a client (medical). I was horrified and notified her immediately. I decided I wouldn't put anything ultra personal on emails from that point on. If I discuss someone (not on here) in an email I try to be vague in case it falls into the wrong hands. Not a bad idea also if you have fat fingers and have sent a 'reply all' by mistake!
And of course, none of you would discuss another member behind their backs on here would you 
Technology eh.