im not sure whats happend?

was going along in 4th gear in a 1.4 8v corsa changed from 4th to 5th up a hill at bout 5000 revs and lost a whole cooling system of water luckily it was cold tonight made it home the car seems to run fine but over heats due to no water, most of the water seemed to be at the bk bulk head under the air box not the radiator dnt think the person behind me appreciated the shower!what could it be?