I'm using a Spektrum DX8 with an AR8000 receiver. It's setup for 6 flight modes and I did a binding to a Failsafe Preset. If I hookup my hexcopter to Mission Planner and shutoff my radio, I can see in Mission Planner that:
1) My throttle goes to 926us
2) My flight mode goes to RTL
However, after getting all this working, I took it out to the field, waited for GPS lock, then lifted off about 3 feet and landed. Then I left the props running at very low speed and carried the hexcopter to a new position about 300 ft away. At the new position, I verified that I was still armed (by lifting off a couple feet), then landed but left the props running on low (so APM2 would think it was still flying). I then shut off my radio. The props immediately quit running. After a few seconds, I turned my radio back on and was able to take off without re-arming --- so the hexcopter was still armed... but RTL never caused the Hexcopter to Return to Land.
I brought it home to look at the logs, but are basically empty, so they were not any help.
Reading the forums, I've not run across any steps I've left out, but there must be something I'm doing wrong.