So apparently, even if you meet the LUK requirements needed to get an enemy Griffon Rider (say, Emilia) to drop an item (say, Ribbon), but you use Flame on the attack that kills that unit, EVEN IF YOU HAVE ALREADY GOTTEN THE GRILLED GRIFFON TO DROP, the enemy's item will simply not drop.
Happened to me today on BF 25. Had to mess around with stuff and Rhia before we figured it out.
This may or may not have something to do with Ribbon nulling status effects though.
PSP version untested for GBA
http://www.twitch.tv/irysa/b/325582486
http://www.twitch.tv/irysa/b/325580734
videos demonstrating glitch and how to fix it