I've found 14 so far, not counting ones mounted in jewelry. All found in CA. Locations like stage stops, after beach storms erode, oldtown sidewalk and demolition tearouts, etc....
To answer Bill's question: They're not found more frequently is is that they were not carried like regular penny, dimes, etc.... Back in the day when $2.50 or $5 was an entire day or week's pay, go figure: That would be like you or I loosing $100 to $500 today. Hence gold coins were usually only brought out for larger purchases. Ie.: downpayments on real estate. Or to buy a horse, buggy, etc......
In the same way that .... today .... when it comes time for you to have to put a $500 outlay on a car down payment, etc...., you generally have a checkbook, or credit card, etc.... Ie.: some other way than literally "500 cash". Yet on the other hand, there will no doubt be pennies, nickels, dimes, etc... in your pocket, right ? Same logic as back then: The gold coins were brought out for when it came time for larger transactions only. That's not to say they couldn't be in people's pockets though (especially during times of travel long-distances-moving, when it's reasonable to assume you'd pack up your savings with you to take).
And oddly, they're found more often out west (CA, OR, etc...), than back east. There's various theories as to why that's true

But suffice it to say, it's anecdotally true: There's hunters back east with SCORES of colonial coppers, busts, reales, large cents, etc.... yet have never found a gold coin (or only found 1, etc...). Yet here in CA, there's lots of hunters that have found 1, 2, 3, or more. I knew of a guy who got one on his first day ever detecting (storms of 1982-83 beach erosion ).