Both true. It's very simple for Five, he's got this all... almost figured out, sure. If he hears about his death he'll probably assume he's alive via time travel nonsense, so feel free to complicate his already insane math with that information.

I could absolutely give him a reason to be by the lake. This whole thing was how it went down with his rude forest guy. He also hasn't really shared that the whole thing happened with the group, so you know. Telling people to be afraid of the wind?? That sounds silly.