Not be blunt, but your friend should probably pay better attention. I dont mean that in a negative way, because stuff like this does happen on occasion, but if it has happened to one person more than once, then a little less BS and more paying attention to loading.
Down at our range if our rifles are loaded we leave the RR in them, if we break for rules discussion, or instructions on the next target, etc. that way there is no guessing. I have my range rod marked at un loaded, and also loaded with different powder charges, I can drop it in and tell at a glance what state my rifle is in.
But I would pull the last load down the barel, and shoot out the first, no sense wasting both.