Favorites list can be cleared due several reasons, and the most common are:
1. If you have added lady's profile to a blacklist then she will not be able to write you new letters only after 24 hours after adding to a blacklist. Old and received recently letters will not be deleted;.
2. Lady cannot be in My favorites and My Blacklist simultaneously;.
3. If lady from you Favorites list was deleted from a website, then she will also will be deleted from My Favorites list;.
4. If lady from your Favorites list was added to My Blacklist, she will be deleted from My Favorites list.
5. If lady from your Blacklist was deleted from a website, then she will also be deleted from My Blacklist;
6. If you will write a letter to a lady from your Blacklist - she will be removed from My Blacklist.
For more accurate information please read this article
https://www.bridge-of-love.com/article-more_about_my_favorites_and_my_blacklist-1192.html
If the mentioned reasons are not the one that caused your lady to gone from the list, please contact website's technical support immediately.