I have an idea of what might have happened. I run the program on two computers, and I believe I might have opened it on the second one before Google Drive synced all the files. Seeing immediately that the changes were not there yet, I closed it right away. However, as far as I understand, the program automatically saves the file upon closure even if no changes have been made, thus the database on this second computer with no changes ended up having a later date than the one on Google Drive with the changes. Then the Drive synced this later databased to the cloud and other computers, and I ended up losing work.
It would be good if the program only saved a new database if something was changed to prevent this from happening in the future.