Hair Transplant - FUT: Will my existing hair cover up the donor scar? (Photo)

Hi, I have decided to get a hair transplant. I am taking a week off from work and I am concerned about it being detected when I return. How long does your hair length have to be to cover the donor scar directly after surgery? Also I believe I have enough pre-existing hair on top to cover the scans as well. Please let me know your thoughts. I would like to be able to leave the surgery with three donor scar fully undetectable. Is this possible and is there shock loss around the scar? Thanks!