you disable Adblock Plus at the addons bar or a toolbar, click on the icon, and choose "disable everywhere" when done uncheck-mark the line. Nothing should disappear from you toolbars or be disabled or uninstalled in add-ons.

How did you disable it, if you disabled the extension itself it will appear at the bottom of the extensions list as disabled, re-enable it and restart Firefox and you you be back. In the extension options once enabled click on Options and check all items there and it will be active, and visible on the add-ons bar. The options list from the Add-ons list is the same as the "preferences" list on the add-ons bar within the icon. The options there is same as the options in the add-ons list menu options. Disabling in the options menu is the same as the item "Disable everywhere". "Ctrl+/" will hide or display the add-ons bar.

Thank you so much dmcritchie! It was there near the bottom of the list just as you said. Now I can go about my business without all of the annoying ads just as before:D