I have had occasion to travel long distances on short notice. Just for the heck of it, I looked up getting from Charlotte, NC to Sydney (as that is a major international airport).
United can book a flight that leaves CLT (Charlotte) at 6:10 PM to SFO (San Francisco) and then to SYD (Sydney), arriving at 8:10 AM. Total flight time is 22:00 hours.
United can also book a flight that leaves SYD at 3:25 PM to ORD (Chicago) and then to CLT. Total flight time is 24:22.
With a total of 7 hours and 15 minutes in Sydney between the flights one could clear customs and meet Australian LE in the airport, exchange papers with all kinds of witnesses and signatures, and head back with papers in the hands of a live human being - who could testify to having them in his/her possession the whole time.
If the prosthesis was found on Tuesday with enough time to get someone to the airport, they would arrive back at Charlotte airport just before midnight tonight local time - total time for the trip 2 days, 5 hours, 37 minutes.
Not saying that's what they are doing, but just that it would be possible.