Finally found the friggin thing. See photos attached. First one shows the general location: it is located inboard of the right frame member, above and behind the rubber suspension bushing. You need a light to find it as it is well hidden, and protected from below by a metal pan.
The second photo shows the drain tube itself. It shows up in the light as the vertically oriented (but angled backward) item identified with the yellow arrow. The end of the tube is cut at an angle so the opening is vertically oriented to the back of the vehicle. It was not plugged. Chances of a plug-up are minimal due to its hidden location, and protection from below by the metal pan.
Anyway, hope this helps if anyone else is looking for this on a late build 2015 RAV4 Limited.