I bought two hydrangeas on saturday,.?

one was blue and the other pink.left them outside overnight and wanted to re-pot them today. They still looked beautiful this morning, they we quite hard and cold ( I guess from the frost) then around 11amish, they had been in the sun for no more than an hour, both plants have flopped and the colour from each plant has totally gone and they are wilted. I am really gutted. Im no green fingers, yet i adore flowers and plants and spent a lot of money on pots, soil and different plants, hoping to make my garen look pretty for the summer. Please if you know what happened or what i can do to revive them I would be ever so grateful. many thanks in advance for your answers.