Maybe you use some kind of cleaner program that would have removed imported files from your system.

By the way, the folder C:\User\username\Appdata\Roaming\eTeks\Sweet Home 3D\furniture contains only imported SH3F libraries. 3D models individually imported are stored in [font=courier new].pref[/font] files in the folder C:\User\username\Appdata\Roaming\eTeks\Sweet Home 3D.