His 'message' is mostly notes on this encounter as well as the surroundings, but if Lirael takes a look she may notice it seems to be nonsense, as it's enciphered.

"No, I'm sorry. I, ah... I was in my library, where there'd only be dogs like this one, and I'm not sure at what point I ended up here. You were the first person I came across."

The unasked question dangles delicately at the end of his answer, an invitation to volunteer her own circumstances. It seems best to use a light conversational touch with Lirael rather than asking too many direct questions of her.