As I understand, it's quite important to know where the item was found. Thieves seldom keep detailed records and hardly any are trained in Archaeology.
1) "Hey, I found two steel gears somewhere in Peru; they seem to be made on a milling machine." - "Well, recycle the metal then."
2) "Hey, I found two steel gears inside of a solid stone wall in Machu Picchu, they opened a secret door; also, they seem to be made on a milling machine." - "!!! (everybody faints)"
Well, of course, true.
But better an ancient statue ends up in some Sheikh’s house and eventually finds its way to a museum, origin unknown, than some Muslim fanatic gets his hands on it and smashes it to pieces.
That’s what may happen to a lot of those Egyptian statues if the fanatics get hold of them. It’s happened many times before, as it did recently with the ancient statues of Buddha, and many Egyptian antiquities probably wouldn’t exist now if they hadn’t been safely hidden from the Caliphate beneath the sands.