well it depends on the state of things then, for example
1. if we're in lylo or will lose during the coming night phase
2. how strongly you're suspected
4. how many think him vouching for you is TMI
5. if he vouched for you when you were about to get lynched. for 5, that does put us both in a tricky situation
we will have to agree on where to go if 1-5 is answered
i can only say it's very difficult to judge someone's play when someone is being subbed in for someone elae, because it assumes that the player in question wod have the same line of thought