This isn't really a bug but more of an argument on whether it's necessary to provision lower PL rewards to players without Forsaken and has been known about for quite some time. The argument being you could buy Forsaken and want that item at 500 so you could hold onto it. You can also pay better attention to the fact that it says [b]"Requires level 43"[/b] and [i]you should know that you can't reach that level so you can't use it or anything else you might infuse it into.[/i] You can't equip things above your character level, so since you infused an item that was above your level into something you were wearing at the time, it is automatically disabled and counts as 0 PL, which is why your PL dropped. Your [b]only [/b]option is to unequip the item and equip something else until you can reach the appropriate level to use it, or dismantle it and use something else. Bungie will not change the level of your current item or hand you another at the level you want.