[mothered]

When I received the package, I don't think it had any traces of having been opened before

For future reference, don't give out anymore details than what you have to - It may work against you.

In this case, simply say that the AirPods were missing and leave It at that.

Should I just wait for them to go back to me ?

Correct.

If they don't reply within a few days or so, get In touch and ask where your claim stands.

should I insist on the fact that the shipping box did not had any sign of being tampered and so that I think that it must be a factory error and not a transportation related thief ?

Do not suggest anything about the events of the shipment - you're not In a position to determine what may have happened with your goods.

Only provide Information pertaining to what you experienced when opening the package.