Sometimes the other trainees might see something but I doubt the drill sergeants noticed anything. There are usually only 12 drill sergeants allocated to a company, so three per platoon, and that's if you're lucky enough to be at full strength. Even then you may have one or two off from overnight duty, someone may be at a school or other tasking, leave etc. It's not uncommon to have one drill sergeant for a platoon of 55-60 trainees. It sounds like this happened right after morning PT which is a particularly chaotic time so i'm not surprised they took that opportunity to skate. I've never seen an awol take their rifle though, he probably would have been discovered sooner though if he hadn't taken it.Where was the senior NCO? This doesn't seem to be an incident without warning signs?