I just went and looked at the CM logs.
11-05-04 23:16:29 Stream14 Bad Guy Damage Stega 1 325th VFG "Checkertail Clan"
11-05-04 23:17:18 DmdGibs Kill Awarded Stream14 F6F-5 The DAMNED SE
11-05-04 23:18:16 Stega End Flight Crashed The DAMNED SE
11-05-04 23:18:58 Stream14 End Flight Bailed 325th FG "Checkertail Clan"
What looks like happened is this.
You and Stega tangled and you shot of a good chunk of his wing at 23:16:19 (last recorded damage in logs). He started going down but was able to hold it and control it for almost 2 minutes (crashes 23:18:16).
However, you then got jumped by another Ki84 and got shot up so badly you bailed from your dying plane (DmbGibs Kill Awarded at 23:17:18).
Now note that the logs don't record when you bail but the fact when you recieve your bail successfully message from the server. Meaning when you touch down on the ground and exit. However, since you took battle damage as soon as your started your bail the server sent a kill message and credited DmbGibs.
So what seems to me happened is that you initiated your bail before Stega crashed. Since you were out of your plane and a kill was credited to DmbGibs .. the server did not credit you with the kill for Stega's crash and registered Stega as a crash and not kill rewarded.