Mlaudisa said:
Had I re-positioned myself to regain line of sight, I would have been able to bring it back, but when it disappeared behind the tower I had no idea if it was continuing on its trajectory and flying further away: I felt then my best hope was to recall it automatically (in other words, I panicked!).
Allow me to offer a technique that may save you in a similar situation:
If you are going to be flying around something tall like this where you might lose sight of the aircraft
(or giant 700' tall coal stacks, over and around bridges, etc), once you have GPS lock, take off, turn to face the object, set your camera straight ahead and go straight up from your launch position. Climb until the highest point of the object
(don't forget antenna, spires, or other structures protruding from the top) are even with
(or below) the horizon. Allow your aircraft to hover at that point, note your altitude, and reset your Home Point with S2. You should see the tails lights rapid flash green indicating resetting the Home Point was successful
(you may need binoculars if you are really high up). Now that you have reset your Home Point at an altitude equal to the obstacle height you can be confident that, should an RTH occur, your Phantom will climb to that point PLUS an additional 20m (66'), allowing you to safely clear the obstacle.