I think the GP was implying that the vault would store a random string, which would be unreasonable for anyone to possibly guess. This isn't either of the facto

I think the GP was implying that the vault would store a random string, which would be unreasonable for anyone to possibly guess. This isn't either of the factors - just a proof you had both of them. The 2 factors are then the vault itself and the vaults password. It should be noted, though, this is significantly weaker than "real" 2FA, as normally that would involve some sort of challenge, rather than just storing a hard secret.