I am using WineStaging v3.19... but the real key is that they are stored in a hidden directory on the Mac, so unless you enabled seeing hidden directories they would remain invisible to you. Open a Finder window and view the inside of your user directory, then use the key combo Command + Shift + "." (the period key) and this will enable the invisible files to be seen in the finder window. You can now navigate to "your user name"/.wine/drive_c/users/"your user name"/Local Settings/Application Data/VNGINE/Tiimestamps/saves.
Hope that helps clarify
(Edit - also just remember to repeat that key command to re-hide the invisible files when your done)