[1.19.2] Shulk Inventory Size Changed, Lost Items

[fatboychummy]

I started up a server running the pack Cisco's Fantasy Medieval RPG Ultimate. A few of my players chose origins like the Shulk or Loki (I believe it was) which gave extra inventory slots that were kept on death. Now, what they didn't realize at the time was that it was only supposed to be 9 slots. Instead, when they chose the origin and opened their origin inventory, they had a "full chest" -- 27 slots.

Of course, they went and stored stuff in what they thought was their legitimate inventory, but now that the server has restarted overnight, it seems they have lost access to the last 18 slots.

I know 1.19.2 is kind of an "in-between" version that may not be developed for anymore, so I'm not expecting a fix or anything like that (unless the issue is still present on newer versions, may be something to test!). I'm just wondering if there is a way to recover the items in those 18 now lost slots?