Anyone know how I've ended up with half used perfume?

I bought a pair of Primark knock-off Ugg boots off Vinted. The shoes arrived with no problems, exactly as described. However, inside one of the shoes there was a small bottle of perfume. Initially I thought "maybe a free gift"? until I actually took the bottle out of the shoe to discover it was missing a lid and half used. I'm not concerned, more so confused. Because it very much seems like an accident that the perfume is there, but the bottle is a cylinder, so surely the seller would've felt the bottle rolling around in the shoe when packaging? It can't be a case of trying to cover a smell, because the shoes were new with tags, they didn't smell like perfume, and a loose bottle of perfume wouldn't work for that purpose. I did message the seller to ask about the perfume but I've had no response, and I already clicked "everything is ok" because everything was okay with the item I ordered. Just wondering if maybe any sellers could shed some light on why or how I've ended up with a half used lidless bottle of perfume?