he got the drop, and you begged him for it. I'm sorry, but i don't sympathise. There are plenty of reasons why he might have wanted to keep it, get it made into the shield and present it to a friend as a gift, sell it to fund his next purchase, hang on to it and use it himself eventually so that he doesn't need to go out and get one later.

Generosity does not need to extend to strangers, if you already have plans for what is rightfully yours. Just state beforehand next time. 'if X item drops, please let me have it, i've been trying to get one.'

Most people will see this, and agree to it before you even start.