Several times now I have gotten one of these items from people for trick or treating. However they are not showing up in my inventory. I know it's happened at least once with the basket and three times with handfuls of candy. They are not in my player trades either.

I only am seeing one Trick or Treating Basket given to you as a gift.

And I see that you have recently opened at least 3 of them.

Did you just have an old stack lurking somewhere in your Inventory that it got stacked into?

Those are candy handfuls I've made myself. I got one basket from TOT you and another from a user, but the one from the user never showed. The candy handfuls I made myself show fine, but when given from a user they aren't appearing in my inventory. The last time I made them I made 2 and opened two, but I'd been given a third by a user that did not show up. I hope that makes sense lol. I don't keep stacks of them around. I can never resist opening them. XD

I don't see any records of anyone else having sent you a TOT Basket other than me from Halloween night.

I do see two records of you having been given a Handful of Candy:

2019-11-09 22:42:27
2019-11-10 00:43:16

Unfortunately, I cannot really track any further than that with how the current item system works for obtaining/using items.