Almost forgot in my "lost things" post & need advice

I ALMOST FORGOT! While rying to diagnose a worsteing vibration and after hauling to check obvious issues, the mechanic was with me and his helper strattling the shaft in the engine room of my 50 Hatteras SF. Whammo! the 3" prop shaft sheered off at the rear strut. I had to replace with a new pair of Veem props and a new shaft but the 35" nibril 5 blade didn't hit on it's deprture so it's in good shape and I know within a 50 yard x 100 yard area where it is. I've had a diver go down 40', put in a stake in the bottom and swim with a line in larger and larger circles but nothing found.
There is a place here that will rent a guy with a sonar who says he'll find it but it's around $2,000. Seeing I've spent $1,200 on divers and it's been sitting for two years, I'm skeptical it it can be found. The diver said it's relitively a flat, featurless bottom so I guess it;s possible. It sheered off 1" forward of the prop so it's laying flat.
What o you think? Is it worth the expensive fishing trip? S&S prop says it's an $8,000 prop and the replacement Veem Stars pair cost me $20,000. I have the matching prop so it would be a great spare set or I could sell them.
What are the chances of finding it? The company is known for using all sorts of equipment for finding things like this. Worth it?

Nobody but the diver knows and I've known him and been friends all my life.
He reported a "hard featurless bottom" here in CT in Long Island sound. I'm sure by this time it's totally encrusted with barnicles.
What to do, what to do??