Note found in a library book

"I don't know when it will happen again. I can't believe you missed it." There's an initial beneath, but I'm not sure what it is (perhaps a "V"?). This is written on the sort of stationery item that salespeople of pharmaceuticals give away free to medical people, and promotes AstraZeneca and Crestor. I found this within the pages of Dreaming in Chinese, borrowed from the library. I'll always wonder about the "it" mentioned twice.