i'm having the same problem with one of my close friends and I don't wanna be so pathetic and ask especially if it is cos of this problem. But it isn't just them, its a few people so I'm thinking they couldnt of deleted me, she also starts conversations with me sometimes. The person also does not show up in the MSN > tools > options > Privacy > view of who is in my contact list and is also not in my msn hotmail contacts. Does this mean Messenger Plus! could have changed all this or does this sound like the person deleted me?
Added information:
-After finding this out, i deleted the person then was going to re-add tommorow, however the person talked to me today (after I did the deletion) and started the conversation. It started with just the persons email address as their display name until it said 'this person is not in your contacts list, do you want to add them?' so I clicked yes. I can't remember if their normal displayed name changed before or after I clicked add to my contact list but according to plus and messenger im still not in their contact list. I wish my brain wasn't making this a big deal