Not too surprising, however you can change it back. With all your Firefox blues since version 14 or 15 I'm surprised you haven't dumped it for good yet.
Seems my Firefox started using Bing for default search after updating to version 16, when you search using the address bar.
Is it possible that the destination-content in your TAB 999 had enough time to change your search engine whilst you were clicking through 998 earlier TABs ?
The new DuckDuckGo addon is pretty cool, but yeah all and all just change your searchbox provider
Is it possible that the destination-content in your TAB 999 had enough time to change your search engine whilst you were clicking through 998 earlier TABs ?