How did Bod escape from the pawn shop?

Bod manages to escape from the evil clutches of the pawn shop owner, Abanazar Bolger, thanks to the help of Liza Hempstock. Liza was once a witch; indeed, that's why she was killed. But, despite her evil reputation, she nevertheless helps Bod escape from the pawn shop, out of gratitude for Bod's wanting to buy Liza a gravestone. As a witch, Liza was buried without a gravestone, and Bod thinks that's just so unfair. So he goes off to see Bolger in the hope of getting a fair price for the valuable brooch he obtained from the Sleer. He plans to use the proceeds to pay for the witch spirit's gravestone.
Unfortunately, all doesn't go according to plan. Bolger and his greedy partner-in-crime lock Bod up in a back room until he reveals where he got the brooch and where they can lay their hands on some more treasure. Thankfully, Liza is on hand to save the day. She utters a few magic words and—hey presto!—Bod slowly vanishes into thin air, leaving Bolger and his accomplice looking pretty confused when they open the back room door and find that he's gone.