Maurice has discarded 8 burner phones. Find all 8 phones to uncover Audio Logs that may shed light to his story. Fortunately, you don't need to look hard and far. Some Burner Phone locations will be revealed if you unlock ctOS Towers in different areas in the game.
You only need to find 7 phones since you'll get the first Burner Phone as part of the story shortly after starting the game. After finding all burner phones, you'll unlock the trophy “Sanity Check”.
The phone is phone inside an old warehouse. Just place a waypoint on the phone and you’ll be able to locate it with ease.
Head to the shipyard warehouse marked in the map and find the Burner Phone on a computer table.
You can find this phone on the rooftop of the Crazy Moose Inn. To reach it, find the forklift behind the inn and use to reach the roof. Open your Profiler to find the phone beside the steel railing.
The next Burner Phone is found in the area of the trailer park. Find the blue colored house and climb to the roof. You'll find the phone on the railing.
The last Burner Phone in Pawnee is located inside the fenced yard behind the Fish and Chips restaurant. Go through the gate and open the shutters to the shed in the corner of the yard to find the phone.
Found in the scrapyard under the highway bridge. You have to climb over the fence to find it.
You can find the phone on a wooden plank on the upper floor of the demolished building.