this bug appears in the Black Lion Trading Company window, it is triggered by moving the items to sell into an invisible bag.
to reproduce this:
requires an invisible inventory bag. the ones that dont show the items inside it, in the selling tabs.
-have many of a stackable item in normal bag, and organize it so as to have it appear last in the item list shown in “sell on trading post”. having it be the only visible item to sell also works.
-open Black Lion Trading Company window, either by the menu, or talking to one of the npcs.
-go to “sell on trading post”.
-select the stackable item, DON’T sell it yet, just select it.
-move the stackable item into the invisible bag in the inventory window.
-choose 1 of the stackable items to sell. just don’t sell all of them.
-click on the “sell” button in the BLTC window.
-click on “ok” button.
-you will now see that the blue bar that used to highlight the selected stackable item in the item list, is still there, without the item being in said list.
I have attached a screenshot showing this remaining blue bar.
