Oh shoot. I think I needed to post this in the BBPress forum. Why do the names have to be so close to the same, just to mess me up?!?!?!
bbp is usually the prefix used for bbPress functions, so when you see it, think of bbPress. BuddyPress uses
Also, just to add, when you see a prefix preceded with an underscore
_ such as
_bbp_activity_id, it usually means that particular function or variable is intended for internal use, and isn’t really part of any API offered. However, it is just a convention and not all plugins stick to it.