What is the name of this book please?

[Peekaboo!]

I'm looking for a book that I had a few years ago (must have lost it from my shelves or something at some point), anyway, all I remember about the book is that the man is possibly called Max and he works in an art gallery. Towards the end of the book, the woman kisses him or something after realizing her boyfriend is rubbish and the guy likes her too but freaks out a little bit and disappears.

The woman starts up a blog/Facebook group to try and find him and it really takes off - featuring in the newspapers and on the TV etc. In the end I'm pretty sure he turns up and wonders what on earth is going on but I don't remember anything more about the book than that.

If anybody can tell me the author or book title or anything it would be much appreciated cause I'm really stuck on this one and it's driving me crazy.

Thank you!!