Student or Learner
Are the following sentences both correct?
1) Apparently, someone has misplaced his/her umbrella. He/she must have forgotten it. I'll try to find one that owns it and give his/her umbrella back to him/her.
2) Apparently, someone has misplaced their umbrella. They must have forgotten it. I'll try to find one that owns it and give their umbrella back to them.
Instead of "the one that owns it" try "whoever owns it."
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.