Can I retrieve files that GoodSync deleted or changed?
If option Job -> Options -> Save Previous Versions of Files is checked (it is by default) then GoodSync saves the last version of every file it replaces or deleted to _gsdata_\_saved_ folder on the job side where it happens (just like Recycle Bin). This is where you can get it form using Windows Explorer. Note that folder _gsdata_ is hidden, so you should enable showing hidden folders in Windows Explorer -> Tools -> Folder Options -> View -> Show Hidden Files and Folders.