Mozilla found an issue with Firefox 7:  after upgrading to Firefox latest version some of the add-ons will be hidden, this can happen when you upgraded to latest Firefox version when add-ons updates are about waiting to be installed, to fix this issue Mozilla released add-on Recovery Tool for Firefox 7 which is a restart less add-on recovers hidden add-ons after you successfully upgraded to Firefox 7 and it removes it self after recovering the add-ons. Mozilla planning to release small update Firefox 7.0.1 to fix this.

If you found your add-ons missing in Add-ons Manager after latest Firefox upgrade, you shouldn’t worry they haven’t been removed. After using add-on Recovery tool released by Mozilla all hidden add-ons will be visible and usable.