Certified GKH Gardening Expert
When plants are brought in from outside, they need to be acclimated. This article will help with that next time you bring a plant in: https://www.gardeningknowhow.com/houseplants/hpgen/acclimate-plants-indoors-winter.htm
Fortunately, hibiscus rebound well to acclimation shock. If you just give it some TLC, it will regrow its leaves (https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/wintering-hibiscus-indoors-winter-care-for-hibiscus.htm). It may not regain its good looks over the winter, but as long as the branches stay green, it will come back full force when you place it back outside in the spring.