there are a few reasons:
a) It's a busy time for ea account servers, so there is some delay in getting them (but if you say it was last week this option is probably no more)
b) The server crashed, and couldn't transmit your points to the account server
c) sometimes if you leave a game before the round ends, your ribbons are not transmitted (but your points are). A bit like being sure you are getting a gold medal, lose connection, come back, only to see the next round and so, no medal.
And try a 32 players - 64 map sharqi in the Mec chopper with a decent pilot. If you are really good with TV's, you could try wake, hit a few full black hawks and hope the round lasts 15 minutes *G*
(I got mine solo-choppering on operation clean sweep when for some reason, no-one cared about getting in the gunner seat).