Gromp XP bug

Not sure if this has happened to anyone else but I was playing Fiddlesticks jungle and started NE gromp at level 1. I had no leash and upon killing the gromp I received no experience points but I still got the buff. I've played thousands of games and never had this happen. I'm not sure if this is champion specific to Fiddlesticks but I thought I would at least post the issue here.