I'm really glad you got your rifle back today, but if you don't remember a squib, and no one else shot your rifle, I'm not very happy. I'm not there so I can't verify there results, personally I would be insulted, unless there was some room for doubt. A rifle squib is much more easily identified than from a handgun. Much higher pressures don't ya know. And either you had a squib, which usually results in a blown apart barrel in a rifle, or SIG is not being honest. Enough said, I hope your 556, gives you much happiness, but something is not completely right here.
Keep us informed.