while I was messing around with my data I unknowingly deleted an important file called "defaultbuslayout.tres". This was an important file because it structured the layout of my buses:
I realized of its important when running my code.
The music and the sound effect were there, but the index of my Music and Effects buses weren't. I thought that maybe the index was changed, but by printing the number of available buses with "AudioServer.getbuscount()" the output was 1.
I tried re-doing the buses hierarchy from scratch and saving the file, but nothing, the number of available buses is still 1.
On my "Audio" section of the Godot IDE the three buses ARE there, and I can still attach audio stream players to both "Music Volume bus" and "Effects Volume bus".