I dont think ppl would use perlite to boost the weight, one because its blatently obvious and two because it weighs nothing, they use sand blasters or glass etching sprays for that, the uk has been flooded with it!
More than likely the perlite got into the plant/buds during a re-pot of the plant, when i turn my pots upside-down to take the plant out of the pot sometimes bits of soil and perlite fall onto the plants and occasionally i find a bit of soil in my dried bud, so i think thats the most likely explanation, especially if they did any re-potting when the plant has dense sticky buds that perlite will easily stick to.
