The Suburbs - Sewers
Artifact #46: Boat Note
As you walk across the beach, Ellie will point out a wrecked boat. Climb aboard and open the bridge to find this immediately inside.
Comic #5: Antiparticles
This is found directly next to the Boat Note.
Firefly Pendant #14
Now drop into the lower part of the boat to find a pendant behind a hanging blue net.
Firefly Pendant #15
While crawling through the sewer, keep your eyes to the right to spot a side tunnel you can squeeze through. Inside, you'll find another pendant by some running water.
Artifact #47: Sewers Note
Make a right at the fork to find a locked gate. Send Ellie through the nearby vent, and she'll get the gate open. You'll find this on a table inside.
Firefly Pendant #16
When you reach the puzzle with the moving platform and generator, hop into the water and swim to the submerged car. Dive to find this pendant just under the surface.
Artifact #48: Trading Note
In the next chamber, open the door on the same platform as the raft. Take out the infected and head into the back corner of the room. You'll find a bunch of supplies, as well as this artifact.
Training Manual #6: Bomb Containment
After the noise trap, head straight forward to the back of this abandoned safe house. There is a rack back here where you'll find another manual.
Artifact #49: Rain Catcher Note
When you encounter the small group of infected, take them out and make a right. In this area full of rain catching barrels, you'll find another artifact atop a covered table.
Artifact #50: Cornered Note
Head up the winding stairs just patch the rain catcher room, and there will be a blue door on your left. Open it, and head into the back left corner to find another artifact beside a corpse.
Artifact #51: Kid's Drawing
This is found in the first large room when separated from Ellie and Henry. Before leaving the room, you'll pass through what Eric calls a "classroom." You'll find this on the bookshelf in said classroom.
The Suburbs - Suburbs
Artifact #52: Looting Note
Enter the first open house you see and head upstairs. Head through the door on the left to find a room with a mattress. This sits on the lamp stand nearby.
Artifact #53: Father's Note
Further down the road is this red brick house. Head upstairs and take the first left to find the master bedroom. This sits on the dresser inside.
Training Manual #7: Melee Techniques
In the same house, a string dangles from the attic entrance. Pulling it will bring down the whole trapdoor, but you can still boost Ellie up there. Do so, and she will recover this manual from the attic.
Artifact #54: Survivors Note
Now enter the house next door and head to the second floor. Enter the bedroom here to find this note by a computer.
Comic #7: Messenger Particle
Adjacent to the same room is a small bathroom. Enter to find this atop the toilet inside.
Artifact #55: Matchbook
Now head to the top floor to find another artifact beside another computer.
Firefly Pendant #17
Right near where the wild dogs are first yapping, you can hop a ledge into a backyard with a swing set and playhouse. This hangs from a tree branch above that yard.