My Firefox updated automatically this morning and all the search engine options on the Firefox toolbar disappeared.
The "restore default" button is also greyed out. Searching the suggested list of add-ons, popular search engines like Google, Yahoo, etc are not listed. All of the default add-ons that are supposed to appear as options on the Firefox tool bar are missing.
Opaite Mbohovái (3)
See cor-el's answer in this - https://support.mozilla.org/en-US/questions/902000 - support thread.
Unfortunately, this answer does not help my problem. I found the "Search Plugins" folder and it is populated. There are seven xml files including Bind, Google Yahoo, etc. in this folder. C:\Program Files\Mozilla Firefox\searchplugins
OK, problem is now solved. Apparently the update somehow changed the folder attributes to "hidden". Changing the folder back to visible restored the search options. If not the update, this could be a remnant of a rootkit trojan I had several weeks ago that changed many of the program file attributes to hidden.
Moambuepyre