The reason is that Holo hates when people fear her on her Wolf form. It's something that she mentions previously on some occasions. When she transforms to save Lawrence on those tunnels, he actually cowers in fear before her, which I suppose makes her believe he won't be able to have a real friendship with her. However, Lawrence realizes this and starts shouting to Holo that he'll not let her go until she pays her debt to him (which is an excuse, and Holo knows it); the reality is he doesn't want Holo to go.

Lawrence wakes up thinking Holo actually left him, since that's the last thing he remembers. But then he receives a letter. The letter is actually a debt he has to pay, because apparently someone bought some clothes and apples while he was asleep and said Lawrence was going to pay for the items. When he read the letter, the apples made him realize it was Holo who bought the stuff, which meant she didn't leave him. So he rushed outside to find Holo in his cart, waiting for him.