Mike...can't say I ever heard of a 100% fish kill unless it was about 4' thick ice. Did you happen to drill any holes? IF it is spring fed, the springs should warm the water and thin the ice also, if there was water flow from them. 8-10 feet is on the edge of the minimum depths needed for your area.

Maybe get a cast net from Walmart, bait some traps and see if you catch anything....