That hot water could freeze before cold water is something people have said for a long time, and there may be a grain of truth to it.
This would be weird because at some time, the teperature of the initially hot water would have to cool to the the same temperature as the initially cold water! (before passing and getting colder!)
I seem to recall someone tried this out by putting an ice tray each of hot water cold water into the freezer and the hot water would freeze first!
One explanation was that the hot water would steam off a lot of its mass, so that by the time the two trays had reached the same temperature, the hot water trays would be left with less water to freeze. At this point, the two trays have the same temperature, so the tray with less water would freeze first!
Is this true? I don't know for sure, because I havn't tried it. But the explanation can impress your friends!
Note that this would not apply to laying hot water on the ice surface. It would work because the two ice trays are in some kind of thermal equilibrium.