Are the books still there, in the sense that the author folder contains a title folder that contains a book file?
Are there any other titles in your library by that same author?
Does the check library function complain about these folders? (IIRC in 0.7.22 that function is available at preferences -> misc. In 0.7.23 it was moved to the dropdown library menu.)
Edit: Any chance you are accessing the same library from both linux and windows? Doing so is a disaster waiting to happen.