Mozilla will update their browser time to time, you also update your browser sometime you may lose some addons. Add-on Recovery Tool Firefox 7 1.0 is a free add-on which will help you to recover lost addons. You can recover all of the add-ons that disappeared from Firefox’s Add-ons manager.
You can simply add Recovery Tool into your Mozilla browser. After the installation process restart Firefox to complete the recovery process. Recovering all of the add-ons, the tool will remove automatically.