Im am amazed the cut last that long, Here in NJ, we are lucky that a cut will last one low tide. Most are gone by the next incoming high tide. That is an ENORMOUS amount of digging. Glad it was all worth it in the end.
When there are that many targets, there it gold hiding somewhere. Glad you found it.
If the diamond is any good, you can always have it re-mounted in another setting or made into a pendant.
Fantastic hunt !!!