If you pull Fyrakk before everybody is on the platform, those outside cannot get in.
When/if you die you get the achieve for dying to him, and when/if the group kills him you you get the achieve, but no ability to roll on loot.
After this the game thinks you have completed the fight, and saves you to a lockout.
Do not think that is a bug. Just you are not in range and did not hit the boss so you do not qualify for loot from him
People suck when they pull to soon
If its not a bug, it shouldn’t save you to the fight.
If you don’t or cant hit the boss in every other case, you do not get saved or loot locked for not hitting them.
Perhaps a range thing, still stupid.
Imagine people afk in that lfr this could be to keep them from loot
They already solved that problem before; you don’t hit the boss you don’t get loot; but you also don’t get locked.
I’d be fine with running it again, if I wasn’t loot locked. Therein is the problem.
As far as AFK people in LFR: no matter how Blizz implements something, people are lazy and will find ways around it.
I just had this happen to me today, I even said ‘not ready’ but they started anyway, kicked another guy who was afk though, I should have just left, putting in a ticket didn’t do anything unfortunately. Hopefully I didn’t miss much loot-wise.
Lame 
At least its just LFR loot, replaced by M0 stuff pretty much.