Case book play

[tempestos]

A referee on a crew of mine read a case book play from the 2003 Rules Differences book that went kind of like this:

A has the ball first and 10 on B's 5. A1 passes into the endzone where it is intercepted by B1. As B1 is being tackled in the endzone, A2 grabs and twists B1's facemask and B fumbles the ball. The ball rolls out to the 2 yard line where it is recovered by A3. The facemask is a 15 yard penalty. Where is the spot of enforcement, who has possession and where is ball placed?

I will tell you that the book claimed that the 15 yards was enforced from the 2 yard line, leaving the ball to B, first and 10 at the 17. I can't see that making sense no matter how I try to put the rules together. I think the book was wrong.

What are your thoughts on the correct answer.