I made a portal and it generated properly in the Nether, but when I returned to the overworld my portal was in a totally different location, and the one I had made was still there, but not linked up properly for my return. I looked under the new generated portal and there was not a ruined portal underneath it either, sometimes while returning from nether the portals will link up to existing ruined portals in the overworld and that is why I checked under the newly generated one.