Not much to add on what has already been said, but a couple of things that I noticed.

Interesting about this Box name. Michael said that he had been there, but he didn't know it. It seems likely if there was a general nickname for it, if you had been there you would have heard it.
So, is it possible it was added after the outbreak. If it was there are a few possible reasons that I can see:
- Made to match the Sandbox name.
- Because that is where the newbies are trained.
- Or there is something more out that has meant it gained the nickname.

I also find Michael's wording interesting as the plane flies off with the other. He says "And just like that they were gone. She was gone. And I was the idiot who let her go".
It strikes me that especially that last part, still sounds like someone that is writing about the past with a bit of perspective. The phrasing to me doesn't sound like something he would be writing on the day it happened. And, could this potentially be some foreshadowing and not just a broken heart talking? If things are good for Pegs in her new location, he is only looking back sadly. But if things take a turn for the worse, then this takes on a different meaning.

...Or I have been hanging out with you crack pot theory people too much and am now reading way too much into things.

P.S. If they find Saul again, he is going to be mad that they took Lady!