Lost spirit skull

I'm in act 3 cruel and fought the big witch. My inventory was full, which I didn't know, and when I picked up the skull that grants you more sorryI spirit it must disappeared and I didn't get any spirit from it. Which is bull crap because that totally screwed this character over.

I ran it again to see if she'd drop it again since i never got it and I'm just screwed out of the extra spirit on this character because it's fine forever.