[Owncloud] Strange deletion - full Folder unsynced

[Niko]

Hi List,

I have noticed some strange behaviour. My OC-Client deleted the content
of a specific Folder. The Folder still exists but it is empty now on my
Windows 7 64 Bit.
If I look on my Server the Folder still contains all my Data, but the
Client doesn't sync it!
Is there any way to "reset" the Sync so he starts to fetch / sync all
Data from Server against my Desktop again?

Thanks
Niko