They were not upgrades. One was the Warbonded Argo pack that had all the Argo ships.
Okay, in that case I take back whatever I posted before and cast dirty looks towards the CIG customer service.
You should be able to unmelt any package you directly bought before for cash.
The only thing I can imagine thats not a complete fail of the shop page would be that they still got their stupid package timers.
I somewhat remember that you only could retrieve special event specific ships and packages a while AFTER the event was through. Or maybe that's just my dementia acting up. Who knows?
Anyhow the customer service should be able to help you find that buyback. Whether you want to use it or not, you should have the choice at least.