What does it mean when someone is in the hospital? What does it affect?
We have two roles that are virtually unkillable – the Master and the Doctor. They have a special ability: regeneration. If they are killed, they don't die but are sent to the hospital. After two in-game days, they return to the game. Also, Sergeant Arnold's ultimate action (prevents the selected player from writing during the day until the end of the game) and Baker's ultimate action (prevents the selected player from using any abilities or special traits until the end of the game) are displayed in the same way.
Therefore, if a player ends up in the hospital, it means they are either the Doctor/Master, or Baker/Arnold used their ability on them. That's how it works.