I did! I did!
You are against having guns in Elder Scrolls. But you want a plot line where a gun is invented but then the technology is destroyed.
An interesting idea, but I still doubt that it could or would be implemented reasonably. For example, what would be the in-game motivation for destroying the gun.
A sligtly modified plot line would be to have a quest to get a newly discovered Dwemer created gun an it's blueprint for some faction (maybe the Dark Brotherhood) as the ultimate weapon. But just at the end of the quest when you are just about to get the plans on how to make the gun, they are destroyed.
Guns did not have one inventor, they evolved over a thousand years getting better and better, the cannons was most useful scaring horses but they soon become effective in destroying fortresses. first handguns was a small cannon you lit the fuse on and held in you hands, no it was not an good idea but later versions was better.
Now the cannons might be useful in the Skyrim civil war but handguns needed some hundred years development before they become effective.
Also first handguns was effective in one setting, you had an large army on your side shooting and an large army of the enemy in thigh formations, guns up to 1830 was so inaccurate you could not aim and shoot an single enemy however if 100 men shot at 100 other you got an good effect, longbows was actually more lethal but they required lots of training while you could train musketeers in an month.