IIRC, Richard I is buried in Rouen.
No, he’s buried at Fontevrault.
Further investigation shows that his heart was buried in Rouen, and the rest of him in Fontrevault. There is a tomb effigy in both places. The heart has since been moved to the municipal museum in Rouen.
You’re right about the heart. Here’s a picture of that monument.
Could you (or whoever told you this rumor) be thinking about King George I?