It's not crown rot. I've never seen this with a phal before. I barely touched the little leaf and thought "that felt loose" so I went to see if it was and wiggled it a little and it popped clean off. It had a little yellow tint to the base of the leaf and where it was attached looked to be dry, as if the plant had sealed off access to this leaf.
Without knowing anything else I would look at that wound and feel pretty confident that the plant would be fine. It looks like it was cut with a sharp blade and has started healing. Knowing the circumstances I'm very curious why the plant would do it to itself.
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Well, it looks like the leaf has started growing again! I don't know what this orchid is doing. I saw no damage to the leaf, it looked perfect! This is what I get for calling this phal a favorite.