ownCloud deleted local data on my machine, data could not be found anymore

Hi all,

We use ownCloud at our university for a save handling of data. For my dissertation I regulary save important data there. I use ownCloud client version 2.7.6. on my Windows 10 machine. For a while sync was disabled. Then I enabled sync for a collection of folders. Next day, when I started my machine only those selected folders where available on my machine. Then I enabled sync for all folders. All seemed to be fine. But then I realized that few important folders where missing on my local machine and also on the server. I thought, ok those files are for sure in the bin. But they weren’t! I cannot find those file in my local bin nor in the bin of the webbrowser. Does anybody could give me a hint where those files have gone? I’m kind of desperate, would appreciate any help.
Cheers,

David