Um? Missing Pop, lock and Rocket acheivement

Hey, FeatherdOrc7 here with a rather interesting delima that has me scraching my head… it seams that when i look in my acheivments listing there are only 49 acheivements (mind me thats without the crimson map pack downloaded)where when i got my LE of Halo 4 i also happened to get the collector’s edition strategy guide by prima which in the appendex listing of all Halo 4 acheivements states one inparticular acheivement that is not on the list of my Halo 4’s acheivements (that is the list on my xbox 360) promptly named “Pop, lock and Rocket” worth 20 gamerscore. now don’t take me for someone who hasn’t looked ive googled it and nothing, ive looked it up here on halowaypoint and nothing it really is perplexing as to why this is that there was no one to my understanding notice this yet now i may just not be looking hard enough or am just blind to that one post that eludes me but, if anyone could provide answers among the community it would be grately appreciated i don’t know if anyone else has seen the list in the collector’s edition guide but, i assume someone surely has or just knows about this acheviment that maybye it took a last minute editing out by 343 that didn’t get edited out the guide… opps i almost for got the way to earn it is on mission five launch the missle into the core at the end of the without hitting any depris, i believe ive done this already but not sure if i did it wrong if that helps out any…

P.S. thanks for taking the time to read my topic guys…