Getting dehydrated and rehydrating, water weight

On Sunday I was away from home most of the day and didn't have good access to water (and I didn't think to take any with me). Honestly I didn't drink many fluids all day. Yesterday I was feeling the effects and drank about twice as much water as I usually do to rehydrate. This morning I weighed in about 1.5 pounds up. I'm not worried about it because I know it's the water, and I stuck to my calorie goals yesterday. But drinking lots of water is supposed to relieve water weight, right? Will that 1.5 pounds come back off if I continue to drink enough water? Or is it water that my body needed and was lacking, and therefore will hold onto?

I weighed in last Thursday and was basically the same as what I weighed yesterday morning.