Determining if an item is in one of a player's collections (possible endpoint request?)

I want to see if a player has an item in one of their Collections, ideally just by providing an item hash. For example, if I have the item hash of an emblem, I'd like to be able to see if a given player has that emblem in their emblem collection. I figured out a way to sort of do this by downloading that player's collection vendors and seeing which items they can "buy", but I found out that doesn't always work since sometimes the player can't "purchase" items they have in fact unlocked (if they already have a copy of a given item in their inventory, for example). Furthermore, downloading all the collection vendors takes a LOT of data and time since they contain so many items. I'd love it if there were an endpoint that did this (pass an item hash, return whether the player has it unlocked), but I am open to suggestions as to how to approach this in its absence. If an endpoint already exists that I happen to have missed, all the better!