Stephen,
Deep Creek Hot Springs is available to the public during daylight hours only, that specifically means that you are not to be at the hot springs and also anywhere along Deep Creek up to 1-mile on either side of the creek.
I do not know where you are getting the impression that Deep Creek Hot Springs is open during night hours.
If you've ever been to Deep Creek Hot Springs, there are signs indicating so.
U.S. Forest Service Regulations are as follows for the Deep Creek Area,...........which includes the hot springs by the way:
No Overnight Camping at the Hot Springs.
No Campfires at the hot springs.
No Overnight Camping anywhere along Deep Creek.
No Campfires anywhere along Deep Creek.
No Glass Containers are allowed along Deep Creek and the Hot Springs.
The U.S. Forest Ranger for that area also has a Sheriff escort him to the hot springs. I know both of them and they will cite you if you violate any of the above.
Stay away from the area at Night. Overnight camping is available at Bowen Ranch,............Not the hot springs!
Some additional advise:
If you intend to camp out at Bowen Ranch, arrive at the ranch at reasonable hour, don't arrive like 12, 1, 2, 3 in the morning hours.