I'm not sure about Spot's thickness... With it being so big and windy, most of it is probably considerably thinner than the other ponds around that area.
But you saw someone out there? I suppose it could've been me... I went out on it in a small cove to the right of the zoo for an hour or so on Tuesday morning. I always fish it at least once a year, sometime early in the morning so if they kick me off, I've already got in a bit of fishing, since the legality of fishing Spot is, err...
a grey area.
But on that matter, I did catch a few dink smallies. First smallies I've caught through the ice