I updated my iMac to Mohave last night, went to bed and this morning found my Insync drive just about EMPTY!!! I have lost hundreds of thousands of photos. I looked at my actual Google Drive account and in the right column see that files/folders have been deleted. I DIDN’T DO THIS!!! WTF is going on???
If you then look in the “trash” folder at the left side of Google Drive, you should be able to restore all the files just like a regular computer bin.
As for the deletions themselves, I can’t say. May be the insyc log files will tell you when and why a deletion occured and where it came from? Just a supposition here.
If that don’t help at all, I would suggest you emailing the insync support directly with the log files included and the most details possible.