Ha! I've finally got a theory! It just hit me on a 34-2 relisten, when Michael goes out for a smoke, they mention 'the french girl was looking for you, i couldn't let her in'....And we don't hear from Riley again....

I'm thinking Riley was coming to tell Michael "I'm finally going out on a mission! to evacuate from Boulder!"

And this means Kimmet sent 'his worst' to get the people out, because he dare not risk his good soldiers on this 'suicide mission'. This is where we meet up with Pegs/Kelly/Lady (not necessarily all, but at least one). Whomever survives will re-tell the story of the others if they die, and Riley will get to them to the rendezvous point, and back in the story! muahahaha!