What’s wrong with this picture?

Alice: “I just flipped a coin [large number] times. Here’s the sequence I got:

(Alice presents her sequence.)

Bob: No, you didn’t. The probability of having gotten that particular sequence is 1/​2^[large number]. Which is basically impossible. I don’t believe you.

Alice: But I had to get some sequence or other. You’d make the same claim regardless of what sequence I showed you.

Bob: True. But am I really supposed to believe you that a 1/​2^[large number] event happened, just because you tell me it did, or because you showed me a video of it happening, or even if I watched it happen with my own eyes? My observations are always fallible, and if you make an event improbable enough, why shouldn’t I be skeptical even if I think I observed it?

Alice: Someone usually wins the lottery. Should the person who finds out that their ticket had the winning numbers believe the opposite, because winning is so improbable?

Bob: What’s the difference between finding out you’ve won the lottery and finding out that your neighbor is a 500 year old vampire, or that your house is haunted by real ghosts? All of these events are extremely improbable given what we know of the world.

Alice: There’s improbable, and then there’s impossible. 500 year old vampires and ghosts don’t exist.

Bob: As far as you know. And I bet more people claim to have seen ghosts than have won more than 100 million dollars in the lottery.

Alice: I still think there’s something wrong with your reasoning here.