Hear me out. What if... WHAT. IF! At the end of kh3, before namine got a body, Riku somehow got Repliku back. So now Riku is allowing Repliku to use his body to pick up and spend time with namine while Rikus heart seatches for Sora. So now Riku is residing in his own heart, trying to connect to Sora. Which Sora used Rikus station to connect to him. So when they meet Yozura, it's in Rikus heart. Also until another body can be made for Repliku.