Anyone else losing desktop bookmarks when syncing with iCloud?

I use a Dell laptop running Windows 7 and browse with FireFox. I've been using iCloud to sync my bookmarks across my laptop, iPhone and iPad, and have started noticing that bookmarks are disappearing. When I find one bookmark missing when I go to use it, it makes me wonder what else has disappeared.

Has anyone else ever experienced this? Is there any way to recover what's missing?