For the pure, ideal Bayesian, everything is "evidence". Given the probabilities that you currently assign to all possible statements about the world, when you observe that some statement P is true, you update all your probabilities in accordance with the mathematical rules.
If I then ask, "suppose I don't observe that P is true, only something suggesting that P is likely true?" the answer is that in that case I did not observe P. I observed something else Q. It is then the truth of Q that I should use to update my probabilities for P and everything else.