Kudos to you for trying to help.
My actual experience with recovering gold with my AT PRO has been limited to 4 Gold Rings. The numbers have ranged from 51 to 65.
I suspect that the quarter sized fraternity pin has already been recovered. A surface target with gold color will attract a lot of attention. Another thing I find a little puzzling is, Who wears a "Gold Pin" during an interactive sport? Maybe it was a Frisbee toss. If he wasn't involved in an interactive sport, was he standing on the sidelines. If the pin was worn on his jacket, (As in Lapel pin), I would focus on the sidelines. Something about this story makes me think
that this pin is long gone. If the pin is still there, it will be a surface find, or probably no deeper than an inch.