[url=http://www.wowhead.com/item=69251/lashtail-hatchling#comments:id=1408995]There[/url] you have a list of all quests from the chain.
I assume you played a Hordie, and if so, you can run this:
If it is as you say then every quest up to this point should be completed./script print(IsQuestFlaggedCompleted(26278))
/script print(IsQuestFlaggedCompleted(26317))
/script print(IsQuestFlaggedCompleted(26321))
/script print(IsQuestFlaggedCompleted(26323))
/script print(IsQuestFlaggedCompleted(26325))
/script print(IsQuestFlaggedCompleted(26330))
/script print(IsQuestFlaggedCompleted(26350))
/script print(IsQuestFlaggedCompleted(26351))
/script print(IsQuestFlaggedCompleted(26359))
/script print(IsQuestFlaggedCompleted(26360))
/script print(IsQuestFlaggedCompleted(26362))
/script print(IsQuestFlaggedCompleted(26386))
Also, an annoying question, but did you set the dungeon difficulty to heroic?