[mothered]

It'll be handed over without any form of verification.

Perfect DNA material.

As far as you're concerned, you didn't personally receive the package.

If I claim missing item, won't I be questioned by the courier?

The carrier's job Is to deliver packages, not evaluate whether the Item was enclosed.

And that they may get authorities involved?

In terms of the DNA, an Investigation may be opened and subsequently a police report requested.

Also is it a bad idea to place my old watch inside and say I got the wrong item?

It can be done, however given you have two methods available (DNA & missing Item), It's best to opt for either one.

Thanks for the quick responses by the way. You've saved me from using the TFID methods.

You're welcome.