Yeah, just tried doing one of my disappeared events with a drop cost (not one of the most expensive ones) again, and had to pay the cost a second time even though I'm already in the event. This really needs to get fixed ASAP. As it is now, I basically can't do any event with a drop cost unless I'm 100% sure I'm not already in it (with me having entered a whole bunch of events during the last few days, this is a bit of an issue), and I can't go back to one I know I'm in and try to improve my result either, because then I have to pay the drop cost again.