Ask a friend to lie for you and you’ve just asked them to trade their word for your mistake.

Asking someone to cover for you moves the risk onto a person who got nothing out of the original decision. If it comes apart, the cost lands on their credibility as much as yours. That is a large thing to request casually, and most people say yes because refusing feels disloyal rather than because they want to.

Handle your own mistake and tell them what happened rather than what to say. If somebody asks you to be the cover story, you can say no and still be a good friend. Those two have never been the same thing.