Bougainvillea dead?

I bought this plant in a 2 gallon pot last spring in Florida's Home depot. Here in NYC, i replanted it and it bloomed all summer into early fall. It was the hardy variety. Temp no lower than 40 degrees. I'm assuming it meant in the ground...which I did not have. Middlee of fall, the it started to go into its dormant stage, and I just pruned it and put into my shed where the temp never got below 40 degrees. Now that the weather is getting warmer I took it out and as a habit, scrape a couple of the branches to see if it exposed any greenery. To me that is a sign that it is alive still. I did not get that result...I did water it a couple of times...but nothing so far. Is it dead? I thought hardy plants endure cooler temps than others.