I'm sorry that you are not getting the information that you WANT but you are getting the CORRECT information none the less. Your piston and liner are ruined! Regardless of how much use is on the engine a particle of debris has wedged itself between the piston and liner and created that gouge. Of course it is perfectly straight because the piston travels perfectly straight up and down. If you remove the liner and then the piston you will find damage on the piston as well. If you continue to run the engine in this condition the nickel plating will start to peel and create even more damage to the engine not to mention it is not going to run well and its performance will only deteriorate as the nickel peels.