While I, of course, have no more idea of exactly what the cause might have been than anyone else, I can say that it is not uncommon for guys to clean a pistol and then store it / carry it muzzle down in a holster or gun bag. This allows any oil or solvent left in the firing pin / striker channel or on thre breech face to "pool" on the primer of the chambered round and, sometimes also on the first round in the mag. CCI's primer sealant is pretty good stuff, but it ain't magic. If something like solvent or a penetrating type oil, etc. stays on that primer long enough, it can penetrate the seal and kill the primer. In fact, one use for WD40 can be to make sure old primers...for reloaders, say...are deactivated before tossing them in the trash.
Did you try and fire the rounds? If they just would not fire, my guess would be something like the above senario. If they fired in a different gun, then maybe it was gun related...or possibly they could have been reloaded Gold Dot bullets in CCI cases and not new ammo at all.