Hey guys, it's R.I.P Yuri here. I just wanted to say that I watched this YouTube video that attempts to explain why Frost is NOT in the mission "Down the Rabbit Hole" in Call of Duty: MW3.
As you guys very well know, Scorched Earth from MW3 is the last mission where you play as Frost. Afterwards, you never hear from him again-ever. Sounds sad, right? Well, this theory states that, according to the canon storyline, there was a one day gap between October 13 (Scorched Earth) and October 14 (Down the Rabbit Hole). Because of this, Derek got some time off because he was probably frustrated with the failed mission to save Alena and went for a drive. However, he was suddenly assaulted and woke up with amnesia.
This also attempts to explain why the character you play as in MW3's Spec Ops missions is actually FROST himself! Yep, you play as Frost in the Spec Ops missions. Because of Frost's amnesia, he has deluded himself into believing he's a Special Ops spy guy (kinda like Jason Bourne all over again) saving the world in the Spec Ops missions of MW3.