The "big chest" is called a "strongbox". There is only one in the game and you can find it in Level 1, in the lecture room.
This room is located near the start of the puzzle-game.

I believe on the second floor, in what looks like a court room

Where did you get that big chest?

Hahaha forgot to collect the most valuable thing in the game, maybe next run

wheres your collection of crack pipes