The key is filling in the holes when you are done. Thus, nobody should see the 7" deep holes.
Seriously though, You cut a horseshoe shaped cut in the turf. Cut it kind of deep if you can and make it adequate to dig a little under. Open the turf like a flap and carefully lay it over on the side. Do not separate it. It should remain connected on the open end of the horseshoe shape. Now, take a towel or something and lay it down on the grass. Dig your dirt out and put it on the towel so that you don't loose dirt into the surrounding grass.
It would also help to have a pinpointer. That is a small hand held detecter ie., Whites Bullseye II. I have the Bulleseye II and what I do is hold a coin or other metal object in my hand. I then hold the Bullseye (substitute whatever pinpointer you have here), about an inch or two away and adjust the sensitivity so that it beeps or vibrates. That should be adequate for pinpointing in a hole. Now, before you start digging, wave the pinpointer over the underside of the flap that you cut. Also wave it over the top of the flap. If you find something, remove it and check with your detector again to see that there isn't something else there. Now, if you haven't found everything there is to be found, dig a hole and place the dirt on the towel. Keep using your pinpointer to check the sides and top of your hole, as well as the dirt that you remove and put on your towel. It also helps to have a tool like a Lesche Predator. That is a hybrid kind of tool that looks like a knife but has a curve in it like a trowel. It is what you will use to cut your horseshoe shaped plug in the turf. It has a serration on the edge to cut through roots and an edge for cutting and the curve for scooping and digging holes. Keep digging your hole till you find the object, or feel that you are doing more harm or whatever for what it is worth.
When finished, dump your towel full of dirt into the hole and clean up the area. Fold the turf that you cut back over the hole and press down well with your foot to tamp it all back into place and re-establish good root contact with the dirt. If you can, take a large bottle of water with you and sprinkle a little over the grass when you are done. I have had a thought that It might help also to sprinkle some Cayanne Pepper over the area where you dug, when you are done.
Might sound a little odd but there can be problems with animals like dogs and squirrels digging up areas that detectors have dug. Pulling up that grass that we cut through and dug under. Seems they can smell the fresh dug soil and their instinct tells them to dig there, themselves, to see what we might have burried. Part of their forraging for food. They don't know that we are takers and not stashers, they think we burried a big bone or nut. By sprinkling the pepper, it might deter them from going near there.
In the end, there should be no sign that you ever dug there.
I did maybe make one mistake and that was to give the guy my name. Since he had no interest in seeing how I did things he probably called down there and said so and so is down here digging big holes all over the place and wrecking the entire park... which of course couldn't be further from the truth. Hopefully that didn't happen.
Over here in AZ I just kick the sand back into the hole! Let the wind blow for five or ten minutes and BINGO no more hole!! 
