Well, if he had all of them before the electric barrier.........
There are secret areas in Zulag One, and those are the same exact ones from the escape from RuptureFarms. So if you got all 28 out the first time, you should know where the Zulag One secret areas are. Hint: Some of those secret areas are closed off, so there are even less. For example, going into the area with the elevator that takes you to the screen that takes you to the Stockyard Escape is pointless, as that one was closed off.
There are no secret areas in the other Zulags, however. There are employee lounges though, meaning out-of-the-way areas, not necessarily hard to find. So make sure you got everyone out of those.
And respect for trying to do the game without a walktrough
