Hello,
It's a bit strange. Void Stone supposed to be given into your inventory from the very beginning of the game. If we exclude a weird bug, there could be two other reasons why that might happen:
1) You installed this mod after you created the world and use it in existing save
2) You use some other mod (aka Easy Start or something similar) that modifies starting inventory and basically overrides its content instead of adding items
Could you please try to temporary disable mods that give you starting items and start a fresh game just for test?
Clarification about snatcher chest and stone mechanics: snatcher chest will produce void catalyst inside itself if you put void stone into it