While I agree with the others that prosecutorial discretion would indicate the federal government is unlikely to spend any money to investigate this, if they do, the proof would not be that hard.
They find the pen. They call the shipper. The hotel says they found it in the room and shipped it. (Hopefully. Heaven forfend if the hotel called
@Rabbitt6968 first and asked for instructions.) All the normal hotel business records come in and they link the room to the OP. Then, I wonder if there are any partial prints or dna on the device?
Do they care? I don't think so. There have to be hundred of thousands of such events every year and it does not make sense for the federal government to investigate them. The current administration has not increased any real aspect of the drug war as yet and poppin' dime bags on the street corner does not seem to be worth their time.
Of course, when the post office sends a post card or calls, you don't acknowledge anything NOR do you go anywhere to pick it up. Remember the key rule, don't talk to the police. (
)
As to the freaking out, as long as you do as you should from this point forward, what else can you do? You can't go back in time and remember to bring your tobacco vape home so they can't confuse it with the cannabis one. You can't stay in another hotel where the previous person didn't leave their vape for the hotel to find even though you missed it when staying there. You can't go back and change the actual facts to make whatever crazy series of events to cause this mixup result in something that can be reasonably explained with just the right story. Really, at this point, what can you do other than STFU? Good thing that should be enough.