I may have found a bug, unless there's something about warp scrolls I don't understand.
I have one warp scroll in the second row of my inventory, given by the Ilari stone (which has since been updated to only provide warp potions). When I used the warp scroll to teleport, a warp potion is consumed instead.
To use my final warp scroll and free up my inventory, I had to consume all my warp potions so that the scroll would finally be used.