Depends on what type beach you're at, and what your objective is. Were you hunting the wet sand, or dry sand? And I'm assuming ocean beaches, or did you mean lake beaches? You gotta be more specific. If you meant wet sand at ocean beaches, be aware that mother nature is constantly changing that zone. Sand comes in and out, and re-arranges with tides and swells over time. So it is entirely possible that you could've been in acres and acres of absolutely sterile sand (as mother nature might have been piling in sterile sand over the preceding weeks). Soft sand, which is soft to the step, is a sign that sand is "coming in". Firm hard sand (so hard you can practically ride a 10-speed bike on it), is indicative of sand getting compressed, drawn out, eroding, etc... And then there is inumerable other indicators to look for when hunting the wet sand, that would take a book to go into detail about: Scallop shapes (damp or wet looking low or "in" zones, where the surf scours down in specific shapes), cuts, slopes, elbows, etc....
Or if you were hunting the dry sand, perhaps you are on a beach that gets pounded to h*ck by other hunters? Perhaps you were doing something wrong with your machine? Perhaps your beach is just lame to begin with (low traffic, etc...)? Wherever people gather, they tend to be fumble fingers. At the very least you should be getting foil, tabs, caps, etc... on the dry, where people lay about and play.