Hey Smellbag0_0,
Progress is stored on the EA account level, not on individual platforms like PlayStation, Xbox, Steam, etc. This means if you link your platform to a different EA account, you'll lose access to that progress and it will appear to have reset. Progress cannot be moved between different accounts.
It looks like that may be what's going on here as well, as you've mentioned playing back in 2019, however the EA account you're currently posting with was not created at that point, and has only very recently launched Apex Legends on any platform. It doesn't look as though this current EA account has ever launched Apex on PlayStation, so we'd need to track down whichever original EA account was used in order to access the cosmetics and heirloom you've mentioned going missing.
We are not able to make any changes to your account status or progress via the forums, but if something was linked or unlinked incorrectly it may be worth contacting support to see if the original platforms can be re-linked to whichever EA account was used at the time.