For all we know you just died quickly after it triggered and didn't even realize it, can't prove that without logs of it not triggering without the debuff up.
I doubt it's bugged. The more likely scenario is that you died before you noticed that it procced or that you took a hit that was more than 200% of your max HP which would make last resort not trigger.
I've not only experienced this with last resort but Holy priests wings as well. Their are times when its cast sub 20% and I have no cds that I just die. Meta never procs, nor does the heal from wings. I don't have logs as this is happening in mythic + but according to both skada and details im not suffering a mega blow that would eat through the heal provided by LR or holys wings.