The Naxxaramas Betrayer that gives you the quest for the Frost Wyrm Lair stone wouldnt accept the quest as finished even though i had 100 naxx servant blood and i quit the quest and lost all the blood /cry

This just happened to me as well. How are we supposed to get into the frostwurm lair if the quest is bugged? Is there a workaround?

Simple, when you raised 100 Naxxramas Servant Blood make a screenshot of them and then ask a GM in-game to give you the teleport stone