Glitch where nether portal disappears when you spawn in and walk out of the chunks then walk back in

Me and my brother have a 2-player survival world and when he went to the nether for the first time he went in and explored for a bit but when he came back to the nether portal I wasn't there. Then he asked me if i could go in and see if it would spawn the portal when I arrived but when I went in I spawned in but there was still no nether portal so now me and him are kinda stuck in the nether.