"Mirrors" is song 2 of 6 played by the guitarist at Iron Mike's Camp in Lost Lake. He turns up at random in the gazebo behind the bounty collector.
Go to the gazebo behind the bounty collector at Iron Mike's Camp. The guitarist doesn't show up every visit, so check back if the gazebo is empty.
It comes right after "Yesterday". "Our Lies" plays next. Each song you hear him play counts as one collectible.
Addy - "Straying From the Path of God"
A Christmas card to Addy from her parents, kept in the infirmary at Iron Mike's Camp in Lost Lake. It is on the upper floor, on a table at the top of the stairs beside a green book.
Addy - "The Old Generator"
A note from Rikki to Addy about the noisy old generator, kept in the infirmary at Iron Mike's Camp. It is on the ground floor, on top of the right-hand shelf before the exit.
Boozer - "My Beautiful Wife"
A picture of Boozer's late wife, Joany, kept in his things at Iron Mike's Camp in Lost Lake. It is on the table beside your own bed in the room you share with Boozer.
Boozer - "Our Only Guest"
A photo of Boozer and Sarah with a thank-you note from her, kept in Boozer's things at Iron Mike's Camp. It is on the table beside Boozer's bed in the room you share.