iIt should have been left in the pool, not removed (IMO). I've never removed one for the winter and have never seen a problem from leaving one in. If I were inclined to remove a light for the winter, I'd at least fully remove it by disconnecting the wire from the junction box and storing it inside. (As an educated guess, I'd say that having it out of the water will allow for 'dry-rot' of the gasket that seals the light, necessitating more frequent bulb and gasket replacements). Call the dudes and ask them why they removed the light (and please post the response, I'd love to know why they think it's a good idea)
If it's going to stay on the deck all winter, I'd put a pad (rubber, an old towel, whatever) under it and place the lens on the pad and cover the unit with a 5 gal bucket. (Hope to hear back from you with the pool dude's answer )