Sounds to me like you’re not including the file correctly. If you were, the function would exist.
Basic integration has very little to do with what you’re trying to do. They are unrelated in most ways. Basic integration just allows cookies to match up, so that you have a unified login scenario, where you can login and out freely from either side of WP or BBP.
Deep integration involves loading bbPress inside WordPress, and WordPress inside bbPress, so that all functions and data are available to both sides at any point.