After just releasing Firefox 7.0 on Tuesday, Mozilla has released an update at version 7.0.1. It addressed an issue some were reporting of add-ons being hidden after an update. The problem is seen in the release notes for 7.0.1 and detailed in a post on the Add-ons blog.
We’ve identified an issue in which some users may have one or more of their add-ons hidden after upgrading to the latest Firefox version, affecting both desktop and mobile. These add-ons and their data are still intact and haven’t actually been removed. We paused new updates to Firefox to minimize the potential impact on users and will soon release an update to fix this issue and ensure all your add-ons are visible and usable. In the meantime, if you notice an add-on missing entirely from the Add-ons Manager, you can use a simple workaround to recover them.
You can download Firefox 7.0.1 from Mozilla.org.