There are a number of categories for items that have been unlocked, and it can be confusing to remember what you have actually obtained. This is mostly in terms of items such as weapon skins.
What I have found is that, after purchasing or unlocking weapon-specific skins, it is very easy to forget which weapon the skin is allotted to go onto. With the rotation system, you have a time limit on memorising which weapon a skin belongs on, and then after that, it is left to your memory.
This is especially annoying when the weapon looks similar to other weapons of which the skin cannot be equipped, and in the early game when you are yet to have access to all weapon types and are forced to remember which skin goes on what gun for an extended period of time.
I propose -to be added when practicable because it’s not a priority- to have a section of the game whereby all unlocks on the account, bought or otherwise, are displayed so that such items are not lost in a sea of weapons that have no skin.