I'd agree that the fibres of the filter are the source of the weird sandlike particles. On the positive side, I believe the golden colour of the filter's oil residue is a good sign of "fresher" oil. It is not even close to being on the black side. I'd get a sample tested for sure. I'd think the oil did get changed by the dealer but with what? Regardless, I'd do it again immediately. I'd too, recommend the fleece filter.
If you get a Blackstone sample, I'd Be happy to let you Compare with my test results (at approximately 50,000 miles).