Zombified Piglins in Overworld disappears after player sleeps in Overworld.

Note:This may be an intended behavior. I'm reporting it just in case it's a bug.

Several zombified piglins ran into my nether portal and stucked in a hole i dug in the ground. As long as I didn't sleep in the overworld, the zombified piglins remained there, but after i went to sleep one night, all of them disappeared after I woke up. Attaching photos won't prove anything.