When my tablet hang up while flying, the log not remained. I flew over 10 minutes without seeing FPV and after landed I noticed it. Result - birds can fly without Pilot app, flight log is recorded by Pilot app (I believe inside the bird there's another flight recorder, but seems not to be synchronized to app's afterwards).
There's an internal SD card - epoxied inside so it's not removable and not user serviceable/accessible.
In theory, you should be able to fly your Phantom "blind" i.e., without the Pilot app. You should get familiar with the lighting array on the outside of the Phantom. They're not just pretty lights - the patterns of the lights, colors, slow flash, fast flash, etc., have meaning.
When the green light flashes slowly, that's the "safe to fly" indicator - (P mode with GPS and Vision Positioning - if turned on)
When the green light flashes twice - BLINK BLINK PAUSE then repeats - that's the "safe to fly" without GPS but with Vision Positioning - again, that's *if* VPS is turned on.
When it's a yellow light flashing slowly, that means it's safe to fly and you'll be in A-mode but no GPS and Vision Positioning. (That's the way the manual words it - don't know if that means with or without VPS activated. I've been flying for a long time with my Vision Position (VPS) turned off.
So, based on the above color scheme - you can fly, whether you have the Pilot app running or not. *And* you can take pictures/videos. You just can't see what the camera is looking at, cannot adjust the camera, etc. But if you keep it close to you, fly visually and carefully, you can still use it. Fly up close and adjust the gimbal where you want it - both wheels will still work and both shutter buttons (the ones on the remote controller) will still work.
It's basically the same as if you're flying and the pilot app dies and you have to fly it back home by yourself. Saying that, I've yet to use the RTH.