I wanted to rename my personal graph. This graph is synced using the beta sync feature. What I did is simply rename the folder and re-opened it in Logseq from the “all graphs” page. Logseq prompted an error saying that this graph was already loaded and then, all of the content disappeared. No history, no files to recover, nothing. My bad for not making a backup before doing so but I lost a considerable amount of data there. I tried reproducing the issue but I did not get the same behavior. It is worth noting that my graph was on my Mac Desktop which is synced with iCloud.
Few steps that would be good for you to try. Can you check the directory on disk, specifically check the logseq folder and see if the files exist on the bak folder?
Also, enable hidden directories through command shift full stop and check the hidden .recycle folder within the /logseq folder.
This could likely be caused by using the iCloud directory for logseq sync, it is advised to keep the two separate.
Are you on the discord? You may be able to get better help on the dedicated beta sync channel.