@Thierry_Coutelier: Apologies for not replying sooner. Your files were trashed by Insync because it interpreted the folder with an empty file as the new state of your Drive files, so it synced the “changes” from your local machine to Drive. The wording could be improved to prevent this in the future.
As for resolving this, please retry opening your Trash in Google Drive as it could have been a temporary issue. If you can open it now please try restoring the accidentally trashed files. After restoring them it should be fine to start Insync on the PC with the intact data. Then on the machine where the data was lost the easiest way would be to restart from scratch. This can be done by deleting the folder
~/.config/Insync then re-adding your account.
When re-adding your account you can try pointing Insync to a folder that already contains the files from your Drive account so that you won’t have to re-download them. For example, you can copy the files from the PC with the intact data to the other PC.
If the Trash in your Google Drive account still can’t be opened then you can try this instead. Restart from scratch again by deleting the
~/.config/Insync folder and re-adding your account but choose a new folder this time. After the syncing has finished copy the files from the PC with the intact data to this new folder so that they will be uploaded to Drive. This will not resolve the issue with your Trash though, and it could result in your Drive account running out of space because the storage in your Trash will still be counted. I suggest that you contact Google first to resolve your issue with your Trash first before trying this.
Hope this helps.