Artifact #66 - Lab recorder
You receive it automatically after the completion of the previous stage.
Artifacts #67 - #75
You will find them in Ellie's backpack after you start the stage.
While trying to find a ladder for David, you will bump into a clicker. Coming out of the room to the left.
The pendant is in that room.
Right after you finish the horseback escape, you will walk inside a cottage. To the right of the building, there is a garden house with the pendant inside.
Artifact #76 - Lakeside resort map
When you cut to Joel for the second time, you will find the map in your backpack.
Artifact #77 - Ellie's backpack
Joel will pick it up automatically after you reach the meat storage.
Artifact #78 - Meat Ledger
It is to the right of Ellie's backpack.