So, I get back to you because we found the problem and it might be useful to someone else. Basically, the F/A-18 was purchased on steam and not on the the DCS World site. That might explain why it didn't appear on the order list. When I made the switch between the steam version and standalone, I had transferred the module. For some reason, it got unlinked. I still owned on steam though, so I managed to transfer it back to standalone and that worked (in the steam section in my profile).
Thanks for the support you're awesome!
