If he got the males out of the room before they released their pollen, then he got seeds because his plants hermd. You might think that they didn't, but get in there real close, get a magnifying glass or a jewelers scope and check things out. I bet you find balls, or at least old balls that have popped open. Balls are always huge and out in the open, they hide in the bud, they can be tiny.
I highly doubt that he got his girls pregnant by rolling a joint. That's like saying your gonna get pregnant from the toilet seat, lol. Unless his bud was sugar coated in pollen.
Think about it... the bud that was seeded was pollinated at least 5 weeks prior to harvest. Since it was originally pollinated, the bud has grown at least twice it's size. Assuming there was absolutely no air flow in the grow room and the pollen just sat on top of the bud. Then the pollen would have to hang on through harvesting, trimming, drying, curing, packaging, shipping, handling, the nug being broken apart to be rolled, hang onto your hands or clothes, then get blown off of your clothes or if it was on your finger tips and you physically touched your bud. I think that it's much much more likely that he's got a hermie or two. Either from genetics, stress, or light stress during the dark period.