I hope Kagi will add a button to this page:

...which would allow us to redirect the failed search to another search engine (e.g. Duckduckgo or Google).
A user would be much happier with your product if you provide convenient way for user to accomplish their main purpose (searching) when your product occasionally failed to do so. I believe that's partially why !Bang exists, and you can take a step further.
Best of all, if user allows, this kind of case might also be automatically send to Kagi to be used as a nice reference to improve search quality.
p.s. I know in the "more" section there are options to redirect, but I do believe additional guidance on the main page will help. Keyboard shortcut would also be nice!