When Paul was playing skat in a dug-out and went to visit some friends in another dug-out, what had happened when he got back?

From the text:

It is this Chance that makes us indifferent. A few months ago I was sitting in a dug-out playing skat; after a while I stood up and went to visit some friends in another dug-out. On my return nothing more was to be seen of the first one, it had been blown to pieces by a direct hit. I went back to the second and arrived just in time to lend a hand digging it out. In the interval it had been buried.