You can check your "reverse list" to see who has you on their contact list.
Tools
Options
From the list on the left (Personal, General, etc) select Privacy
You'll see two columns:
Allow list Block list
Underneathe that you'll see Contact lists with a clickable button called "View"
Click on it, that tells you everyone who has you on their list.
If people you want to have contact with are not listed, fire them off an email.
You COULD check
this site too it basically scans your list and reverse for you and tell you what contacts on your list no longer have you listed. I don't know if I would trust it fully myself as for some reason, I recall awhile back reports of people's accounts getting locked out of the .net server for whatever random reason. I think I've checked it once myself and nothing happened, but I can't remember.
Hope that helps!
*cheers*