Facebook uses a simple Search feature. When a person is a member, their User Name is automatically added to that Search database on Facebook. This database is also used in Google searches, such as if you use the search term Facebook+User Name. If you can no longer find that specific person in the Facebook Search database, the person may have:
It means to no longer receive messages from that person
It means: That you are giving a chance for them to lose their Facebook
it means that the person is not actually using facebook at that time they are on a next site but their still signed in facebook
Uncool person or jerk
It is no longer available to you or the public. If, however, you've deleted the Facebook account this means that all the information is deleted permanently.
Some people like to hide behind a computer screen to be mean to other people. Facebook is an easy place to be mean, even for people who are nice in person.
Maybe the account got deleted??
It can mean many things. But chances are that the person is having problems in a relationship.
It means they have customized their privacy settings so you can't see anything they do on facebook, but you are still one of their facebook friends.
It means that they are no longer interested in you. They have moved over to someone else they find more attractive.
it means to send a private message on facebook between you and the other person so not everybody sees it.
it means to organize your wall with all the post of a person together