You havent been scammed.
That implies that you lose something and the scammer gains something. Your bike isnt of the type a Thai would covet.
Nor has the book been sent to Bangkok , just the Phuket "Satanee Grom Garn Kon Song" , meaning Phukets Department of Land Transport Office... its near Immigration.
This is just Thai incompetence.
Go back to the guy and ask him for his help as kindly as you can. Hopefully you have the original owners written name.
My guess is that he sees you as having a farang name , but the sleeve ( not inside the book ) is still labelled in the old owners name and is amongst the hundred or so books he always has in his filing cabinet.
If that doesnt work ...
I'd even offer a 300 baht bribe for him to look into it and find the book , payment on delivery ..as if he finds it , then it saves you a lot of footwork.
If he cant/doesnt find it , then contact the previous owner and have him on speed dial when you report to the Patong Police what happened . Go from there...
I cant emphasize enough how polite you should be with the original idiot , because if you arent , there will be no help.