Some of the roots that provide water may have been cut off or it may be located in a place where it gets either too much wind or sun. Any of those could contribute to leaf wilting. Think transplant shock. Mulch the plant well and maintain the soil soil, not wet. Consider a temporary wind block and/or sun block if the hydrangea is in a sunny/windy location. Do not fertilize. Some leaf loss is to be expected but let the plant tell you. Some form of root stimulator (medium strength of less) mixed with the next watering might prove useful. Half a capful of liquid seaweed with 1/2 gallon of water can be applied on the leaves as it is food that the leaves can absorb while the roots recover. Do this only when watering and discontinue after the plant has recouperated since watering the leaves promotes fungal leaf diseases.