In regards to the basking, I can't speak for frogs, but I have observed basking behavior in Notophthalmus during winter time. Granted, completely different family, but at least its another amphibian. In regards to the second observation, I racked my brain and could not think of something similar. If I had to hazard a guess I would say pheromones still present in the water, but I have absolutely nothing to back that up. Something to ponder.

Alex