Someone seems to have messed with the search tab. For better or worse, I use Google most of the time, The search tab used to default to Google. If I occasionally want a different search tool, e.g. Wikipedia, I would use the dropdown list. Now it seems to default to the last used search tool. How can I get rid of this "improvement"?

It seems that most times Firefox does an update, it deletes the Amazon UK search tool and does not provide any option to put it (or any Amazon tool) back. Where is it on the list of search tools?