Skins have disappeared

After the upgrade, I found loads of additional skins listed under the modified skins view. I also noticed that some of the skins I modified before the upgrade, e.g. login skin, do not appear as a default skin. Yesterday, these additional skins disappeared from the modified skin view. Could someone please explain/answer the following for me;

1. Why are all these additional skins not listed under the default skins view? Is it a bug?
2. Could you please reinstate these additional skins under modified skins until they are correctly listed under default skins, as I would like to modify the forgotten password skin?
3. The modified skin view now correctly lists only those skins I have modified, but why is my login skin not listed under default skins as well? Another bug?

Thanks in Advance for your answers.