after you use a anti ward, you should not be able 2 use that item again, or purchase another. once the round ends, if the item had been used, it would be removed from your inventory and at the start of the new round you had the spot open again.

if you take an anti ward, and use it, you're not supposed 2 get a vacant item spot that you can now purchase another item with, that slot is supposed 2 be full/in-use till the next round hits, which is when the server would manually retract it from your item list... if you had used it.