It would be rather weird scam saying that instead of poster they got a clock ........?:| :^O

How was the tube addressed; did you stick a label on it?  Could it have come off and somebody stuck it on the parcel with a clock?  That would be interesting to see the photos.

I think that if they leave a FB saying "instead of poster I got a large broken clock", there would not be much of a problem to remove it.