We'll keep our fingers crossed for your hydrangea. If it blooms this year, maybe you can post a photo to get it identified.
I received a potted hydrangea for Mother's Day one year with no name. I planted it in a large pot since I didn't know if it was hardy enough. Later identified it as some German cultivar that's only hardy to zone 6 or 7. It spends the winters in my little hobby gh.