u/markforephoto

I need some engine advice. I have a fresh water cooled Yanmar 2GM20F. Earlier I found all my coolant in my bilge. I took off my heat exchanger cleaned it and changed out all the gaskets and put it back on. I just checked on the coolant and it’s all gone replaced with Raw water. I have no idea where my coolant went. Has this happened to any of you? Would you know what could be the cause and how to fix it?