SPCHR(id) outputs 0 when the sprite wasn't defined using a template

SPCHR(sprite) outputs the definition number that was used to create a sprite. But if you made the sprite using SPSET id,x,y,width,height, or something, it outputs 0, even though 0 is a valid definition number.

SPSET 0,7
?SPCHR(0) '7

SPSET 0,0
?SPCHR(0) '0

SPSET 0,112,0,16,16
?SPCHR(0) 'also 0