Hi Cherokee, could you check at the bottom of the "Search" panel of the Settings/Options page.

There should be a box listing the installed search engines. The ones with a check mark in the left column display on the drop-downs.

If DuckDuckGo is still listed, you can click in the space to the left of it.

If it's missing, is the button below the box labeled "Restore Default Search Engines" enabled (not grayed out)? If so, click that to bring back all of the built-in search engines.

Success?

I should have mentioned this link: Change your default search settings in Firefox