Hi, Sam-
1) I just doublechecked by running the command here, and indeed I do get a filtered time series of low frequency fluctuations (LFFs) when I run it by default; the file is called PREFIX_LFF+orig. Can you check and see if you have that? You should. A lot of output files have similar names, so it might be lurking in there... If not, what is your version of AFNI ("afni -ver" on the command line).
2) The PREFIX_LFF time series *is* the bandpassed data.
3) Are you running 3dRSFC on residuals (which I assume that you would be)? Then I don't know that you should need any further regression/projection...
--pt