I think that when it comes to failing with the vendor its important to ask why. Was the product not what they expected, and subsequently lost of interest? Or was the vendor disappointed entirely and pulled its funds. Losing a vendor is tricky if you are relying on it to stay afloat. Finding a new one can be challenging where as losing one of many is not as detrimental to your progress.
Failing regulations is a bit different. I want to say it hold the fate of your product. You need to consider why it failed. If it easily fixed then great, crisis avoided, but if it sets you back then it would be wise to have a back up plan for what to do.
This is why the execution phase is so important, as my colleagues have suggested.