Lets say you are flying into the US with a luggage full of commercial goods (which always need to be declared). However when you reach your destination you find out that the airline has left your luggage at the origin airport and you won't have it until tomorrow. In this situation, how are you supposed to make a customs declaration?
Note that its also possible that the luggage is completely lost/pilfered, so you cannot even guarantee it will eventually enter the country in question.
I was in the same situation a few years ago, so this is from memory. Filled up usual custom declaration (on a machine). Waited for my luggage, went to claims desk and filled up the airline form. On this form you need to indicate if you have any dutable goods. I indicated so, the airline told me that they will not deliver my luggage home - I will get a phone call when it is delivered, and would have to come back to airport and clear it through Customs myself.
When passing the Customs, I presented the declaration and the claim paper from the airline, and was referred to the second screening. The Customs officer at the second screening asked a few questions about the nature of the goods, made some notes, and said I'd have to come back. It was delivered next day and I got a call from the airline. Came back to the airport (there's a CBP office on Arrivals, you do not get to the actual baggage carousel area). I think I filled up another declaration and signed some other form, signed the airline form confirming I got my bag, and got my bag.
Again, this is from a few years ago and related to SFO airport. No idea how this would work if you have a domestic connecting flight.
