Black velvet evening gown with emerald lining

I lost my black velvet evening gown yesterday around 3pm. It's an Allure brand formal gown, size M, with an emerald satin lining that peeks out from the front slit, and a silver crystal brooch on the left shoulder strap. I last saw it outside the Hotel Northampton on Main Street in Northampton, Western Massachusetts, near the entrance by the valet stand. The gown is in great condition; it means a lot to me, as it was a gift from my sister for her graduation, and I would be really grateful to get it back if anyone found it.