This The Last of Us 2 Walkthrough for Chapter 3: Seattle Day 2 - St. Mary's Hospital explains how to get through this short story moment. There are no collectibles in this section.
St. Mary's Hospital Walkthrough
Enter room 606 and open the drawer in the backroom. Examine the document on the table. Go through the red door to the right of the firefly graffiti. Go through the grey door ahead. Finally, approach the firefly duffle bag. A cutscene will play and lead into the next section: Seattle Day 3 - Road to the Aquarium.