I am a level 47 and I was so happy to have completed the monthly challange and recieve 17k worth of experience. With that I had reached 9k over level 48 and was a step closer to reaching level 50 (which I happen to be looking forward to). I turned off my xbox and decided to take a break. I hopped on two hours later and found that all of the experience was gone, yet it says that I have completed the challange. I played another game in the hopes that it would be given to me again and everything would be set straight. That was not the case and now I am left with no 17k for the amount of time I put into playing Halo 4.
Happened to me to. Was at like 32k/34k when i quit 1 night, the next night i logged in to play and was at something like 15k/34k… 