Since the OFFER thread seems to be dead, are you starting a new one, to see how long it will go? If you feel that you can and should grab and run, then do it, and not listen to anyone here. You already know what you are going to do, but then please post photos of your cache.
I doubt if you need to call from a pay phone, or pay a hit man or any of these extreme measures. But as I remember, you are not one for face to face talking. Just remember, if you do a night raid, you might be pretty embarrassed if you get caught, might even make the 6 o'clock news! "Old man tackled in front yard, as he recovers his coin purse that his mommy gave him".
Just tell the owner that you buried some coins when you were a kid, and wondered if they were still there. How much simpler can it be?