Following defeating the ender dragon for the first time, I punched the egg to teleport it to the surrounding endstone to break with a torch. However, it teleported one block to the side and fell into the portal, making it vanish. I've searched the end island, my respawn point above ground near the portal, my spawn point, and the 0,0 of the world. The egg is simply missing. This happened on world seed -2632585794981082264 on 1.16.1 of the Java Edition.