Last I remember, a hot bath (or hot meal for that matter) wasn't a survival issue.

If they have food of some sort and water, they have enough for now. If they aren't getting any food or water at all, then that'd be a problem.

72 hour kit is plenty enough to make other arrangements. It is meant to get you by until you can find a way out of your troubles. It is not meant as a shelter in place indefinitely kit. If they are in Houston, there's plenty of places to go and get necessities, and even quite a few luxury items, including a hot bath. If they are in Galveston, they should've listened to the warnings before the storm hit.