If you ever worked on a bottling line you would realize that is a fairly common occurence. The line is supposed to have a detector to kick out the partially filled cans, something apparently went wrong there.
If you still have the can, you may want to write Coke (include all the codes on the can)-maybe they will send you something, like a coupon for a free six pack, or something.
I had a friend who worked at Millers years ago. Back then, they sold these short fills in the company store to employees (sold by weight of the case at an incredibly cheap price). We used to take these on "camping" trips, but with a half dozen guys you would need at least two trunkloads of beers. In the morning we would have an incredible mountain of empties.