Or there was plastic stuck to the machines used to sample and it contaminated the area during sampling. Or there was plastic in the lab during testing. Though potentially those should have been ruled out by testing a blank sample and a control sample of just the 'empty' sampling equipment.
Maybe there's plastics stuck to the things we detect plastics with?
I should really give the scientist some credit, but I think this is a funnier outcome
Or there was plastic stuck to the machines used to sample and it contaminated the area during sampling. Or there was plastic in the lab during testing. Though potentially those should have been ruled out by testing a blank sample and a control sample of just the 'empty' sampling equipment.