I've tried it, and it doesn't work. Not when the people involved don't know where the item to be found already is.
This argument came up in my group of friends when my uncle claimed that drowsing works. It just so happens that I have a really good place to test this with. I have a water line running from a well that was laid 43 years ago, and I know exactly where it runs and it does not run in a straight line to the house (it actually runs at 90 degrees from the house for over a hundred yards, then turns to the house). The 4 acres yard has been re-leveled and re-sodded several times over those years, used a pasture for cattle, and had a in-ground swimming pool at one time that has now been filled in.
So, this summer I got a few friends of mine together for a BBQ along with my uncle who claims to be able to dowse for water. We gave them each 3 markers and a pair of drowsing rods, one set made by my uncle (that everyone shared), and one set made by them (each made their own out of whatever materials they felt was appropriate). Then I set them lose on the yard. They each put their markers on the ground where they 'dowsed' the water, and then I and my dad (who laid that line by hand 43 years ago) went and checked.
The end result? No one got even close to the real line. No one was within 30 feet of it in fact. We even plumbed down in each spot to make sure they didn't find anything else that we had forgotten. Nothing. Afterwards my uncle even laughed and said that he should have known the line ran that way because he remembers that there used to be a barn with a shower over there.
So, 5 people, one claiming to be experienced, 3 tries each, and not one hit. Now what excuse?