I think it is exceedingly likely that he has gone into rehab for real.
My theory is that the entire last few days have basically amounted to an family intervention.
Doug realized weeks ago that his brother was not going to stop binge drinking and using crack. He disappeared to Chicago to put the rehab plan in place, book the treatment center etc.
Kathy and Lisi were enlisted to put Rob in a room with crack cocaine, and "Unnamed" was there to film him getting loaded, and leak the footage of Rob huffing on the pipe in a matter of a few days. That's why there's 6 minutes of footage.
Rob of course had no idea his brother was going to force him into rehab, and is no doubt cursing as we speak, as he enters the long night of detox and drying out.