Surprisingly, perhaps, the situation is not at all hopeless. You can always recover from a zero-preparation situation and sometimes it can even lead to a better outcome, provided that you know how to do it.
Pretending to be ill or saying that the dog ate your speech might get you off the hook, but long term this will work against your credibility. Your best approach is to go ahead but to use a lean approach to crafting a brief but powerful speech.
Here’s one way to solve the problem:
First of all, throw away all of your old notes, slides and other materials. It’s tempting to try to recycle old stuff but you will find that trying to find and adapt existing things …