I'm newish and I've been doing a lot of cooking; and if I have a food related thing that I haven't needed in a recipe for a while I will move it to my vault.

But now looking, there are things that I am pretty sure I never used or moved to a shop that seem to be gone. If it was just one or two things I would put it down to imperfect memory, but now it's up to 4-5. Looking at the "lock" function does this mean that any of my stuff not "locked" could be subject to just vanishing?

I'm just confused.

no, items shouldn't disappear from your inventory on their own. is it possible you inadvertently used them in a baking recipe? some recipes have ingredient categories that can be fulfilled by multiple different items, and the dropdown menu may have auto-selected one of those items without you realizing.

sorry to poke in here but whats this cooking you talking about ...

baking/cooking is a form of crafting you can do at Fantine's Bakery (the little white house in Veta) where you can combine ingredients to make various foods. baking raises your baking level, which unlocks more items to bake.

If you mouse over the "Personal" tab (at the top of your screen) and then click on the "Account Search", you can try typing in the missing item and it could possibly say where it's located on your account. It won't work for situations where you sold, deleted, or donated the item (or used it in a recipe), but it will let you know if your pet ate it, if it accidentally went into a gallery, etc. That might help.

Perhaps your inventory is full? It doesn't show items over 100 (for basic users) or 250 (for gold account users).