Well, I do not know if I qualify as a seqular humanist... but if I saw a ghots or pink fairies, I would ask: What gives. Then I would make sure that I am not the only one who sees these specific ghosts or pink fiaries. Then, if I can ascertain that also other people are able to see these ghosts or pink fairies, I would probably conclude that they are not supernatural, but natural. Of course, then I would wonder why nobody had described, measure or recorded them before, ... and, in the end, I would probably win a Nobel Prize for the first description of pink fairies, and I would live happily ever after as the first and foremost authority on pink fairies... live would be good.
By the way, what would you do if God appeared to you and proved to you that he/she does not exist?