Progress on this achievement is shared account wide.
Find 20 of the lost treasures hidden throughout Pandaria.
Title Reward: <Name> the Relic Hunter
Lost and Found
One Man's Trash...
Is Another Man's Treasure
This achievement line awards 'the Relic Hunter' title.
There are 28 different items you can loot for this series of achievements, the majority of which are BoA. These can only be looted once per character, after which you will no longer be able to see the related quest item when it spawns. Unlike the items for the Treasures of Pandaria achievement line, these items are NOT always available and will require some camping/luck to find them all.
Since looting these items completes a hidden flag quest, the easiest way to know which item you have/haven't looted is by running the following script:
Simply replace FLAG_ID with the appropriate quest ID listed in brackets next to the items below. The script will return 'nil' if you haven't looted the item, and '1' if you have.
Note: Some of the names for the FLAG quests don't match the items they reward. This is because they gave different rewards during beta and where simply re-used when Blizzard changed their mind about what rewards to give.
List of Treasures:
Valley of the Four Winds
Happy hunting! :)
Thank you for posting this! I was dreading the thought of needing to back-track in order to get the achievement.
Just to clarify one small matter: looted items that vary by class can also be determined by spec (where applicable).