Had a .22 semi-auto malfunction on me and fired five or six rounds full auto on accident. Looking back, it might have been cook off, but I've never heard of a .22 having that issue.
Was it an AR-7 Survival Rifle by chance? The older versions seem to have had a fondness for getting worn sears and going FA on unsuspecting victims.
And I don't believe a .22 semi-auto could ever produce enough heat to cook anything off. I know Mythbusters did tests with live rounds in an oven, and it was nearly 400+ degrees before the lowly .22LR finally cooked off iirc. I've never gotten any firearm to 400 degrees.
On topic, I need to visit Knob Creek sometime soon.