Why did a couple of my избранное disappear? I wanted to see them and they were gone :/

Two possibilities: it's a bug, или the content was removed from the site.

It's pretty easy to tell which is which: if Ты can find the content again - it's still on Fanpop - then it's a bug and Ты should Сообщить it (use the "contact us" link at the bottom of the page. For еще detail about reporting bugs, refer to link). If Ты can't find the content again, then it's probably been removed from the site because the content was either broken или inappropriate.

There is a site called link that will track your Youtube избранное for you. If Ты enter your Youtube username, it will save all your favorites, and any time Ты go back it will let Ты know if any are missing from last time and offer alternatives.