Hellboy: [Offering a beer.] Here. Drink up.
Abe Sapien: Oh, no, my body is a temple.
Hellboy: Well, now it's an amusement park.
Hellboy: Can't.Smile...Without you.
Abe Sapien: I like this song, you know.
Hellboy: Yep I'm gonna need a beer too.
Prince Nuada: We die and the world will be poorer for it.
Johann Krauss: Nice baby.
Baby: I'm not a baby. I'm a tumor.
Hellboy: I know; I'm ugly!
Answer: The hand never fully detaches. It still has the chain connected to it when it was crawling back at the beginning. It simply crawled back until the chain finally drew itself in long enough to pull it in faster than it was crawling.
Garlonuss ★
Yep that's a good answer. In the scene at the museum at the beginning of Hellboy 2, Mr Wink punched the two security guards through the door, but his hand was still attached to the chain, it never completely disconnected from the chain or his body. Then the hand turned itself around and started crawling back to wink, at which point the chain zipped the hand back up to Winx' wrist.