I was flying in my normal location where I've logged probably 80 flights this summer and was in full control of the Phantom. Next thing I know I simply lost control. It was in ATT/GPS mode and doing fine but when I switched it to full GPS mode just to make a smooth return to where I was standing (like I've done countless times) something was very wrong. That's when it started it's unguided decent in a different direction as intended. I noticed that right away. I never lost orientation and never panicked. As it came down I did everything I've trained myself over and over to do to recover. Initially I tried to flip back into GPS/ATT mode and briefly gained enough elevation control that seemed to only leveled it off as it kept flying horizontal and to the right from where I was standing. As it was skimming a few yards over an apartment complex across the highway I tried to go into full RTH. At that point I lost it behind some trees, never to be seen it again. Hard to explain that helpless feeling. Spent the better part of the next three days searching the area. I'm pretty sure everyone in the complex knows me now as well as any politician. I may still be up igh in a tree near the sight because the leaves are still on. I may go back as the leaves start to thin. My curiosity is still fresh. After speaking with the local hobby shop explaining the fly characteristics I observed it appears I may have been a victim of a solar flare. Apparently others experienced the same loss of control in the area that day at the same time. When I lost sight of the Phantom I looked down and had a little over 3 minutes left on a fully charged battery when it started it's decent so it wasn't a low battery. I've got into a routine of checking each battery for full charge before using it. Bad news is I lost my Phantom, my Stella Gimbal and a GoPro 3. Good news is I've upgraded to the Phantom 2 vision plus. Guess my brief stay here in the original Phantom forum was pretty short lived.