I would imagine you would've landed it back on the Threshold and managed to use the remaining airspeed to taxi it back to the hangar?
Quite the opposite I suspect he would have gone for +-15degrees out the front.
And more than likely have done a lighting quick fuel tank change as well as ramming the mixture lever up as well if he hadn't trained the student to have there hand across both anyway.
There is a technique which I have seen from students of a certain intergrated school which loosens off the frictions apparently to reduce wear or some such rubbish while on the ground and doing engine checks.
And the turn back is a very American procedure the UK has been banging it out not to do it to instructors for the last 10 years. But initial training nearly always win's when the poo hits the fan which is why those initial ppl lessons are so important.
I have run a tank dry on purpose 3000ft over a runway to calibrate a dip stick. The engine picks up in under a second once the tank selector is turned. The mixture getting caught by accident either by a jacket or a finger is a pretty common one which is another reason to get students to hold their hand under the lever across both the levers during takeoff. Then when they put there hand down to get rid of flap if its being used they won't catch it.