You forgot to answer on the important first question in my posting. Has BYOND ever worked for you? If the answer is no, there would naturally be no such folder, as it is only created 'on the fly', soon as you log on BYOND the first time.
If the answer would be yes, then I'd say search for 'BYOND'-folder globally on your HDD. You should find two. One where you installed BYOND, the other in your own document's.