The friends in the face book disappear suddenly and we cannot find them even after searching for their names in the list. If their names do not appear in the list it means that they have carried out account deactivation in the face book. If their names are there seen in the list then it says that they might have deleted your name. So, it will not be fine to ask them for that as they would have removed your name in their friend’s list.
If you see that your friend has disappeared from the list, then their account might have undergone suspension or it might have been disabled. The names of the friends in the list are removed to include only the close friends and members of the family. If the friends who have disappeared from your list are available in the list again then the face book might have ceased to be friends with you or the face book might have made some errors.
Sometimes, it might happen that some friends appear when you login at one time and they suddenly disappear when you login again after logging out. When they have disappeared at one time they will appear again without creating any request for the friend. This is experienced by many people using face book. They have an opinion that there is some problem with face book. But, this might also happen when there are several members in the list and the list is very long. The friends who are active or online will get highlighted in the front and those who are offline will be listed later. Sometimes, if the list is very long the names will be listed one after the other and those that come later will be hidden. Their names will appear only if you specifically search for them.