I don't know a thing about Firefox accounts, but I'd be shocked if FF lost your bookmarks. My profile has a bookmarks backup folder in it. I bet you have the same folder and a backup is in there. Post a new question "How do I recover my FF account Bookmarks after my computer crashed". Someone will know how. Make sure you save your profile to a location outside of app data or wherever it's located. A thumb drive would be a good idea considering your luck with computers. Mine is in a FF folder in My Documents. I add the date I saved it for reference. Wait for help or you may never see them again.

Sorry you had that problem. I can only speculate that you had a "perfect storm" of failures; new laptop and having it replaced twice, and somewhere along the way "somebody" screwed up and your data disappeared.

rehan1104 said

... I was logged in to my firefox account when the laptop broke and then I was worried that all my passwords and bookmarks are in there. When I asked the store workers if they wipe the HDDs of the returned/exchanged electronics, they said yes. ...

I'm just speculating here using the order of events as you posted them ...

If they got the returned laptop working AND wiped your data from Firefox while Firefox was running [instead of deleting the Profile folder], AND Sync was still enabled - AND that laptop was able to connect to the internet while they were working on it, and thus was able to connect to the Sync server; that could explain why your data disappeared. It probably was deleted bit by bit from the Sync server, while they were deleting that data, AND when you turned the latest replacement on at home, Firefox connected to Sync and saw no data to 'sync'.

Overall, it's a shame that you lost your data - but Sync wasn't intended to be used in the manner you used it to begin with. Is was made to keep Firefox data synchronized across multiple devices; and the event of a device going dead, your data would be on another device in addition to the Sync server.

They say that "hindsight is 20/20"; IMO, connecting the latest laptop to Sync before you left the store and allowing that device to "restore" your data might have prevented your "loss of data". AND if you then Reset your Password for Sync immediately after restoring your data, that "last return" device wouldn't have been able to connect to your Sync account and wipe your data, as I am speculating as happening to cause your data loss.

In conclusion, when "switching out" one device for a new one, backing up your Profile is the way to proceed to prevent losing data. Yes, Sync does work [some of the time] when "swapping out one device for another", but it's too easy to make a mistake and end up with no data - vs having a backup of that data - just-in-case you hit a "perfect storm" of failures - hardware and human in a situation like this.