For 8x8 sprites:
- $2000.3 sets which pattern table the sprite graphics are taken from (0=$0xxx, 1=$1xxx)
For 8x16 sprites:
- $2000.3 is completely ignored
- the pattern table is determined by the low bit of the sprite tile in OAM
So if you have an 'odd' sprite tile, it will draw from $1xxx... but if you have an 'even' sprite tile, it will draw from $0xxx.
You probably have an even sprite tile, which means you are drawing from the wrong pattern table, which is why you are getting a blank space.