Mine has done the same. I have watered it but I think the very cold weather in Feb has killed it. It came from a neighbour and hers, which is in the ground, is fine so I'm guessing the bamboo roots got too frozen in the pot. I'm going to cut it back (and use the canes in the garden) and get a second lot, which I'll protect in future cold winters.

whats happend is your bamboo has got root bound and theres not enough root to feed the plant . bamboo is very tough so its not the cold . hence the nieghbers in the ground being ok . i would put it in a strong bucket with the bottem cut out thats buried to within an inch of the rim to stop it spreading to far as it can be a real thug or buy some membrane from a specialist that is 30cm wide that you also bury the same if you want your bamboo bigger .any shoots you can put in a pot and weight for it to root and sell or give it away as prezzies.unless its clump forming i would definatly do this to save problems later.ow and water well.