This just happened to me last night. I found that if I logged off and then restarted the game the portal was there. However it took me to the overworld coordinates for where I was in the nether not the original portal I went through.
Fortunately, I had a nether hub so I built up to level 120 and headed for home. I know have a really, really long tunnel in the nether.
Any chance this was fixed in the update that dropped today?
Nintendo Switch Bedrock 1.17.2 also showing same issue.