Hi, sorry I would think they are gone. As you do not speak of another device which you could recover them from that you are Sync'd with It appears from your question, that you are using Firefox Sync as a back up service. This is not what Sync is designed to do. The Firefox Sync service takes a copy of the data you wish to include and transfers it to a second device (typically a mobile device such as a tablet or a telephone) running a copy of Firefox. The storage in between all attached devices is both temporary and fragile and is not stable enough to be (and is not designed as) a reliable backup service. If you have a copy of your Firefox profile for desktop Firefox, you may be able to recover your bookmarks and other data. Please have a read of these article. *https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles *https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer If you have a copy of your data on a mobile version of Firefox, please follow these instructions to connect it to Firefox Sync to copy your data. *https://support.mozilla.org/en-US/kb/how-do-i-set-sync-my-computer#w_connect-additional-devices-to-sync_ Please let us know if this solved your issue or if need further assistance.

Do you have any backups available if you check this in the Bookmarks Manager (Library)? *Bookmarks -> Show All Bookmarks -> Import & Backup -> Restore *https://support.mozilla.org/en-US/kb/restore-bookmarks-from-backup-or-move-them ---- If you use the Time Machine or other backup then try to restore file(s) from this backup. *http://www.apple.com/support/timemachine/ *https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile