I loaded up my usual world and my inventory, gear and contents in my ender chest were items that were from years ago. I only know this because of tools that I had made back then and named were now back in my inventory. For context, I died and lost those items years ago (they were named very specifically) so to see them was certainly shocking (nostalgic though). Luckily I had saved a copy of my world and once I loaded that up, it was 100% correct.

I can only assume this is a result of the bug I have been seeing posted on this forum of players loading up and noticing that their levels, inventory and chests are all empty/zero. Maybe because my world is older it had an older save it reverted to?