I have purposely mis-assembled my Ross, just to see how that worked. (My Ross is unmodified, and has no riveted bolt)
Anyone experienced with a Ross would recognize immediately that something was wrong. The bolt is visibly different in appearance when out of battery it's 3/4 of an inch shorter, or there abouts. For the uninitiated, and certainly for someone who did this under fire in a trench, I could see it happening, but no experienced firearm owner should fall victim.
On my rifle, just getting the bolt to go back on the rails was more difficult than usual.
Getting the bolt assembled in the wrong place was however easier than I was told it would be, in fact, on my rifle, it goes together wrong, easier than it goes together right.
The big safety key, is to watch the bolt head as you push the bolt home. If it rotates 90 degrees, all is good, if not, DON"T SHOOT!