There has got to be some confusion here because you cannot Prestige in Private Matches because everything is unlocked from day 1 and you do not get Experience Points. You cannot Prestige without experience points to get you to the level you would normally Prestige at in online Multiplayer. Private Matches are used for fun only not XP.
Its not like Combat Training in Black Ops where you get "fake XP".
If you still think you DID prestige then post your Gamertag and someone could answer that question.
I told you I do NOT play online so I don't have a GT and I play in split-screen private matches.
Well you just answered your own question. You must have a Gamertag to move up in the game. Even IF you were able to prestige up in Private Matches. Beside you may notice that you only get an option to prestige if you are signed into Xbox live. there is no menu for prestiging in Private Matches.
SOMEONE hasd to have a Gamertag for you to be able to play this game and allow it to count.. Microsoft will not allow any player to play with a Gamertag on any portion of a game unless their Gamertag was signed into Xbox Live.
when you play in splitscreen someone needs to have a Gamertag. Even if they have a Silver account which does not play online you still need a Gamertag.
So in your case then since you do NOT have a Gamertag then you were a GUEST which will NEVER EVER get XP in a game. Nor will that guest ever be able to prestige. Even if the freind you play with has a gold account.
So what was the name of the Gamertag you were a guest with ?
For example. Even in "offline mode" or Single Player or Private Matches you will have the "main player" signed in Xbox Live (silver or gold) . Lets say his name was MyGamertag. Well as a guest which it sounds like you were you would be called MyGamert(1). and in that case you cant get XP or move up in the game.
Even if the main player was playing online in a game and you were a guest you still cant prestige as a guest.
You cant even GET a token for this game unless you have an Xbox Live Gold or Silver account.
Any other regular on the forum want to explain it better ?