Sam Iser asked:
Why does the mishnah use a Zavin for who no one would know that he is a zavin while the man who lost something is rejected for the very same reason? Thank you for your time.
The Kollel replies:
The Mishnah allows a Zav to cut his hair on Chol ha'Moed because everyone knows that he is a Zav, since a Zav is Tamei and must avoid coming into contact with others who try to keep themselves Tahor at all times.
M. Kornfeld