Guild Wars 2

when i entered the instance and obtained the item ’ Tassi Box’ i accidentally dropped it and could not re enter the instance to complete it
then i assumed it meant i could continue the quest
i cant even go back to the scene of the crime to start over Ellen Kiel, she just talks to me about the clues and where to check
so i then went and looked up a guide on dulfy and i am not getting the dialogue i should be getting when i talk to any of the npc’s
Vorrk in Lion’s Arch (Ogre)
Morraloo in Bloodtide Coast (Quaggan)
Kasparak in Gendarran Fields (Skritt)
Trembling Song in Snowden Drifts – Lost Child’s Sorrow Camp
Astorra in Caledon Forest – Rowanwoods

this achievment ‘Every Piece Matters’ seems to be unobtainable for me

Even if you “dropped” the item there should still be an item in your inventory. Unless you dragged the item out of your inventory and destroyed it of course. You could try putting the item in your bank(assuming you didn’t destroy it) and try talking to Ellen again.

it was not in my inventory, my Inventory was full when i entered and Ellen still just talks to me about the clues.