I guess the whole chain of events from start to finish.
Was on my elementalist, wandering through Lion’s arch, when I came across Mad King says. Figured I’d join in, seems like I arrived near the end of the whole thing.
Only got bronze, no other reward. Heard people talk about some key fragment, so I looked again to see if I had anything anywhere. Nothing.
Swapped to my ranger and decided to come back later. Returned again for another round of MKS, got gold, and 2 key fragments. Noticed it appeared as a daily chest in bottom right. Also noticed the tool tip indicated that you could get up to 3 fragments a day.
About 4:30 eastern time, new build. Logged out, patched, logged back in. Noticed MKS was running again. Figured I’d hop into it to get the last fragment. Got gold rank again and… got nothing.
Found a helpful mentor who explained to me that if you got 12 “stacks” you got 3 key fragments, as you get 1 fragment per 4 stacks. Looked at my buff area, noticed that on that 3rd run, I had indeed 12 stacks (which had yet to expire).
Checked my inventory, still only had the 2 fragments from the MKS before the new build. Checked the bottom right of my screen, no chest.
Figured it must have been on my elementalist then, so I logged back onto it, looked around for any fragment that may have been pending claim or been claimed and sorted weird in my inventory due to my bags, nope, nothing.
Seems like I won’t get another chance at it before the daily reset, but looks like I got capped out at 2 keys for some reason.
Update:
Went back for one more run before the reset on my elementalist (the same one that originally got bronze but no key fragment). Again got 15 stacks, again no fragment.
Update 2:
Managed to relog onto my necromancer into an LA overflow and noticed there was a MKS still going, jumped into it. 10 stacks at the end, still no 3rd key fragment.