This sort of stuff does happen. I knew of one company whose insurance limits them to something like 20 containers per vessel. During the Han lunar new year they the would place as many as 35 onto a single ship. One of these would be bound to be on top, especially if you can somehow determine when they entered the loading dock relative to other containers on the vessel. They'd probably get zero coverage once the insurer found out they'd overloaded too.

"Hacking" might not be an appropriate term here though. Most shipping website security is beyond awful. I've used Selenium to pull stuff off of shipping sites before as APIs are almost non-existent. When they do exist, they return fixed length text that you have to decode or you're using something archaic like automated email replies when you email a container number to them. (I have sent thousands of emails in a five minute period to a single VOCC to figure out if they were actually the ones shipping something and where the cargo is.) Lastly I've actually sent emails to website support on tracking sites telling them they weren't sanitizing inputs at all. Zero interest or chest pounding brush off reply.

As for barcodes, they probably mean shipping container number (ISO 6346 - https://en.wikipedia.org/wiki/ISO_6346).

Now all you need are pirates with a Russian Mil Mi-26 to dig for the buried treasure on the vessel while at sea (like in William Gibson's Spook Country)