Part 107 UAS pilot reported a lost link during flight. The pilot lost Visual Line of Sight (VLOS) while getting closer to the UAS and reestablishing a link with the controller.

Narrative

I (remote pilot in command; one manipulating the controls) was flying a Phantom 3 professional within Class B airspace outside my office. I have my recurrent part 107 certificate. I received LAANC Authorization; approved by the FAA for up to 100 ft. as I was within 2 nautical miles of ZZZ. It was a clear day with some calm wind. I just got the batteries updated on my Phantom 3; and wanted to make sure they were updated properly and that the aircraft would be able to takeoff. I flew around my office building in a residential area to make sure that the aircraft was working properly. I did my usual checks (which include flying the aircraft in all directions; up; down; left; right; forward; back; and yaw left and right) and the aircraft was working properly. I took the aircraft up to about 30 ft and took some pictures. Then I walked over with the aircraft to some railroad tracks about 300 ft away from the building. I took a few pictures of the tracks and noticed a cool water tower nearby. I decided to get a bit closer to it to get a picture. I had line of sight (including being able to tell the orientation of the aircraft) and was not over any people; cars; or buildings. I switched to video mode and was able to get a video of the tower. I still had line of sight and at this moment I lost link with the UAS. I remained calm and pressed return to home which I had set before the flight and made sure the Return To Home (RTH) was set to a safe altitude and path. However; I did not see the UAS moving. So I remained calm and tried to get a closer look as to what the UAS was over. It was over a grassy area next to the tower. I made sure to stay far enough away from the tower with the UAS for this reason. I tried to get the UAS to reconnect but I was unsuccessful. There was nobody else at the office so I had to figure out how to solve this issue myself. I was on the north side of the tower and I was unable to get to the drone from the north side; so I went back to my car outside the building and drove to the south side of the tower as to get there faster than if I walked. I arrived at the south side of the tower in about 2 minutes from losing link and the UAS finally connected back to the Remote Controller (RC). It was at this moment that I was able to bring the drone back down safely. However; I did lose line of sight with the aircraft in the process; but I was unsure of what else to do. I had to get to the south side of the tower in order to get closer to the UAS in hopes of regaining connection. Everything worked out fine and I was able to safely recover the aircraft without any accident or injury. I learned a few lessons from this event. The first one being; to slow down and evaluate every move I make more carefully. I should have landed the UAS and done an assessment of the possible issues that could arise while going to take photos of the water tower. I did a quick one in my head which included staying far enough away; keeping it away from people; buildings; and cars; and keeping line of sight. However; I did not take the time to think about what I would do in the event of a lost link. I wish I had slowed down and taken a moment to think about that. The other thing I learned was to keep more of a buffer between my max altitude and what I am actually flying at. I kept the UAS at 90-95 feet at maximum. When I lost link I am unsure of if the drone went any higher than that. It looked like it was hovering pretty still but I don't want to risk that next time. I will try and stay lower in my height range. Lastly; I learned that when flying somewhere that is not within your immediate location; it is smart to bring a visual observer along even if you plan on keeping line of sight. I could have had the visual observer keep an eye on the UAS while I went to the south side of the tower to hopefully regain connection. This way if something changed; they could have let me know. Overall; I did not do anything that I was uncomfortable with; but I wish I had done some things differently. I learned a lot from this experience. Although I was nervous for my first lost link; I am proud of myself for remaining calm and handling the situation well. I learned a lot and believe I am now a more experienced remote pilot because of it. I hope others can learn from this experience as well.