Ah I see thats what caused it Marshall you didnt mention how in your PM .
May I sugest weighing the hose with something then at least th\at way your safe in the knowledge that at least it wont happen again.
Your lucky that you caught it in tme and your koi were lucky to have survived it .
Plumbing is the weak link in any pond especially where a hose is above ground and over the surface, make doubly sure that your pipe joints are all secure .
Chalk this one down to experiance its about all you can do , however you can set about making sure it doesnt happen again my friend
Dave