Yes this is a bug, ive already put a post in the helpdesk (obviously only i can view it) but Agatio said he is going to patch the bug in the next patch he releases, but i didnt get a time frame on when this would be released. but yeah i had the same bug, shows the arrows run out and cant use any skills but you can auto attack, and if you get some of the same arrows again to replace the ones that poofed. they suddenly reappear.