Unfortunately your experience is not unique. I've been a prospector for over 30 years, and I've seen a whole lot of theft and larceny perpetrated on unwitting, honest folk by unscrupulous businesses and scoundrels. Yes. I have bought "pay dirt" with no gold in it. I bought it at a reputable nationwide "outdoors" store in Colorado,, believing a store with a reputation of standing behind quality products wouldn't have anything to do with a "shady" company. Yeah, right !
Seeding, or dropping gold into the pan of an unwitting victim is also very common. Pay to pan operations across the country employ this deception routinely to keep tourists engaged in panning. Criminals also use this devise to trick those stricken with "Gold Fever" into investing thousands of dollars into mining equipment they never intend to buy, nor does their land contain any gold. These thieves are usually well known to local law enforcement authorities and are ignored, even befriended by some.
There is also a ton of gimmicky mining equipment advertised on the internet that is either astronomically overpriced, or makes untruthful claims about their product. Take for instance the popular product "Clay-B-Gone", which does dissolve clay, but as I am about to prove is way overpriced. Just out of curiosity, I contacted the archeology department of Tulane University and asked them what they used to emulsify and remove clay from artifacts. All it takes is a simple mixture containing a fee ion of hydrogen and a free ion of fluoride. I asked him, "Where do you find those"
He replied, "take a gallon of water, squirt a tube of fluoride toothpaste into it, and add a bottle of hydrogen peroxide. Cost ? Around $2 dollars a gallon. Compare that to the cost of an 8 ounce bottle of "Clay-B-Gone".
Production sluices are also a rip-off. For a prospecting sluice, I simply use what is referred to as a "poop tube" sluice. It's just a common ribbed plastic piece of irrigation/landscaping/sewer pipe sold at Walmart for about $3 dollars a foot (sawed in half). For better stability you can glue this into a rigged piece of 1/8th inch PVC (sawed in half of the same length). This works as good, or better than any Keen sluice I ever bought. It also has the added advantage of being super-lite and not being bulky.. which is critical for back country excursions.
Expensive classifiers sold on the internet are also unnecessary. You can find alternative classifiers in the kitchen department of any size, both in metal and plastic, in any Dollar Store in the country. Cost ? About $2 dollars apiece.
Looking for an inexpensive way to separate black sand from gold without spending too much ? It's called "Winnowing", and all you buy is a piece of sturdy canvass. The classified dirt is dried in the sun, and a small quantity is then placed in the middle of the canvass and flipped into a breezy wind. The lighter black sand blows away, and the gold falls back onto the canvass. That's how the Ole' Timers used to do it. Again, the folded up canvass has the advantage of being portable and it allows you to work in the field, instead of transporting the heavy, bulky, unseparated material in buckets back to the house. Which in my opinion is as important as the low cost. The canvass is also a "dual" use item around camp. You can use it to haul your food up between two trees as a precaution against marauding bears and raccoons at night.
If you are going into the wild country, I recommend you buy a small spray can of WD-40. It is a wonderful product. Cost ? About $2 dollars. Sprayed into a gold pan, it will lubricate and help separate fine gold from other material just as efficiently as high priced internet products of the same ilk. If you sprain an ankle (not uncommon in rough country and around creeks) it can be used to relieve the pain. It penetrates and removes moisture. I use it for arthritis as well. Your clothes and tent zippers won't get stuck anymore, and with a lit bic lighter in front of it.. It makes a heck of a standoff weapon in a pinch. WD-40 contains ether and is highly flammable. Even on the dampest, or coldest day.. your fire starting aggravations are over. I've even sprayed it on hooks as bait (the trail of oil attracts catfish, a trick I learned in Louisiana, and a useful survival strategy). It also works as a temporary emergency substitute for gun oil if you need to clean your gun after firing it.
The one internet product I whole heartedly endorse are "Razor Hog" gold mats. I've used them for years to construct my own sluice boxes, and they are absolutely incredible and work as advertised. They've really turned the gold mat into a science. !00 percent recovery ! Particularly on fine flour gold. Their web site is very informative, and explains the science of hydrology and why their mat outperforms their competitors. The mats are also affordably priced, which in my view is very generous on the part of the owners of the company, who could be charging a whole lot more for an excellent product.
Just thought you could use some helpful advise from an Old prospector. Good Luck Friend.
Maybe you could write them and ask? 
