The reason people think there will be water is that when water evaporates on the moon, it won't be instantly lost. Instead, it will bounce around for a while be

The reason people think there will be water is that when water evaporates on the moon, it won't be instantly lost. Instead, it will bounce around for a while before it is (probabilistically) lost. If/when it hits a surface that's below freezing point in vacuum (~200K), it can instead freeze and stick to that surface. There are believed to be such surfaces in permanently shadowed craters on the poles of the moon. They won't find any in any place where the rover can charge, but they might do short trips into shadowed spots, I don't know.