Life's tough. Better though than "I got rammed, I died", I suppose. And here you are to tell the tale. Suggest it's worth raising a support ticket. Had another NPC finished off the kill you should still receive the bounty if it's within n seconds. Given the NPC ended up dead (from ramming) if you'd been shooting it up to that point, then a kill's a kill.
On the other hand, one pilot's ramming is another's tactical decision. And doesn't it take two to ram - did it ram you, or you ram it... hmmm.