What do you mean when you ask if a stock would "disappear"?
If a company was destroyed in the course of a war, like if they had one office and it was bombed and there was nothing left, they might well go bankrupt and the value of their stock drop to zero. In that sense a stock could "disappear".
In general I'd expect that stocks in companies that suffer damage to their assets from the destruction of war would go down. Stocks in companies that produce weapons, supplies for the troops, etc, would likely go up. Stocks in companies that produce consumer goods would probably go down because wealth is being diverted to the war effort.
Beyond that, what happens would depend on the details of the war. If, say, a war was fought in a place that is a major producer of copper, world copper supplies would presumably be disrupted. Companies that use copper would have problems and their stocks would go down. Companies outside the war zone that produce copper would see greater demand for their products and their stocks would go up.