I have beaten a couple mega bosses but never got a keystone

[OrangeCactuss]

I have killed a mega swampert while fishing in the swamp and I did not receive a mega ring. I was just wondering if this was intentional and i am supposed to aquire it some other way or this is a glitch.i do not have a screenshot of this happening but I have the achievement of killing a mega boss

 

[Ayla2656]

Sorry for the very late reply, if you are on a rivals server so Diamond/Pearl/Platinum or Ruby then you already have it. It will be in inventory on the left hand side of your pokemon is an arrow click that and you will see your keystone