Searches default to last 30 days, so you might try switching to All Days and then searching.
And yes, people can delete their themes.
They can also rename them, which can make it harder to find.
For future reference, either adding a theme as a Favorite, downloading it as an .ase, or just creating a copy of it are all good ways of making sure you can get back to the themes you like.
Thank you Carey.
I just made an account and can now safe my themes not as before. New to kuler .
Thanks a lot again.
Greetings from Belgium,