bougainvillae bonsai

Hi,My Bougainvilla Bonsai plant has no leaves remaining.Can I revive my plant,its not dead I think,thanks.

How big is it and why did it lose it's leaves.

My bougies will toss their leaves if I let them get a bit too cold or a bit too dry. They generally push new leaves a week or so later. Mine are all small even though I have had one of them about 20 years - growth in a pot in a northern climate is slow.