Question: I know there is a fallacy in this, but I can't spot it
I would say that both of these are not fallacies, rather just demonstrations of poor critical thinking skills (or applications of "faith"). In the first example, the person is claiming that just because we would not be a witness to the event in question, that no evidence can help determine the probability of the event, which scientifically, historically, legally, and theologically is completely wrong. For example, if I claimed that when I was five I rode a unicorn to Saturn, we can weigh the likelihood of that being true to alternative hypotheses (lying, dreaming, etc.) based on what we know about the world and people.
In the second example, this is just an example of someone substituting faith for critical thinking. One of the problems with this is that "it was a miracle" can be used for anything, and therefore, anything can be assumed to be true. Consider my ride to Saturn when I was five. It was a miracle. Of course, this wasn't written in an old book so those who think their old book is infallible and literal believe they are justified in their miracle claim. But there are literally hundreds (perhaps thousands) of "holy books" that all contain wild claims that are mutually exclusive so without going back to reason and critical thought, we have no way of evaluating the miracle claims.