I had a very similar experience with a Kadet Sr a couple of years ago. Normal preflight and takeoff. I was doing some slow circuits and lost throttle response (dead spot on servo pot, I guess). I was flying at less than 1/3 throttle with a 60 size engine and 12 ounce fuel tank. At that fixed engine speed, it wasn't coming down soon. Too fast for a ditch into the weeds so it was a question of whether the fuel would run out or it would get dark first. I think it took 35-40 minutes to run out and the sun was pretty low. Deadstick and a great Kadet floater landing and one ditched servo!

Ross