The flat earther(s) knew what they were talking about - didn't they?
How many hard-core ball earthers do you think have ever lifted a finger to try that experiment themselves?
It proves the ship did not go over a curve; rather, it "disappeared" because of water vapor, dust, etc. in the air.
The 'effect' being seen has more to do with the way we 'see' with our eyes than anything else. Utilizing higher-power magnification caused an "effective" drop in the
density of the water vapor, dust, etc. in the air - thereby, allowing you to see further.
You did a good thing by checking it out for yourself.