Clock hands not moving

I have a Seiko QQ 611 T with a new battery but the hands are not moving.

I can hear a sound every 5 seconds indicating that the cogs are moving.

I opened the case but not careful enough and a piece fell out, and I don't know where it belongs. Also the alarm clock hand is offset now and triggers ~5h relative before the hour hand.

⏎

Does anybody know what the reason could be that the hands are not moving and where the missing piece belongs?