I can't get a copy of an item from the player's inventory

I am trying to spawn a dropped item entity of a random item in the player's inventory.

I have a variable that's a random number from 0-35, which works, as I have it replace the items of a random inventory slot to something else, which works just fine.

I'm using the block "Get a copy of item from slot (random) of Event/target entity if it has inventory." Which is not working.

I'm sending a debug message saying whatever it is returning: "0 air" every time.

It is neither the random number nor the Event/target entity that is the problem (I'm pretty sure).

How do I fix it, or is there another block I can use to spawn a dropped item of an item in the player's inventory?