just noticed throughout my playthrough of the campaign i have yet to find the c.e.l.l. apc. I do not mean the suv or the apc featuring the tank turret.

I am referring to the one seen in the trailer were alcatraz rips off its turret to shoot the attacking gunship.
I have seen it in videos of the crysis 2 cry engine 3 sandbox editor on youtube and I am quite puzzled as to whether I have simply missed it or if it was not kept in game.

Any details of the level it is on would be appreciated

There is exactly one in the entire game.
It's in the beginning of the level "Gatekeepers", when the Ceph attack a small C.E.L.L. outpost.
One of those APC's (called "Repressor APC" if I remember correctly) comes to help them and positions itself near the exit point that you have to get through so that you end up either sneaking past it or blowing it up.