The Father's note is an optional artifact in the brick house on the second street of the Pittsburgh suburbs. Go up to the second floor, enter the left bedroom and pick it up from the dresser.
A father heading out for food leaves his daughter in charge of her younger brother. If he is gone longer than a week, she should take the boy to the Pittsburgh quarantine zone, keep the door shut, save bullets and move low and fast.
It is not part of the Ish series. It adds one more family to the suburb, separated and waiting, on the street where Joel's group spends its last stretch in Pittsburgh.
Antiparticles
Antiparticles, issue 11 of Savage Starlight, lies on the console in the bridge of the wrecked fishing boat on the beach at the start of The Suburbs.
Boat note
The Boat note is an optional artifact on the bridge of the beached fishing boat at the very start of The Suburbs. Climb onto the deck, step into the wheelhouse and grab it from the console beside the Antiparticles comic.
Bomb: Containment
Bomb: Containment is a training manual on a shelf in the sewers of The Suburbs. It makes nail bomb blasts 1.5 times wider.
Cornered note
The Cornered note is an optional artifact behind a door near the sewer ambush site in The Suburbs. After the runner and clicker attack, climb the stairs, go through the door on the left and find it on a bench by the bodies in the corner.