Arrived at takeoff point 30 min before sunrise. Unbeknownst to me there was another drone pilot at the site tucked off down a path behind a fence and trees. First 2 flights no problem. In the middle of third flight my quad out about 700' seemed to be moving without my control. I looked up from the transmitter and I couldn't find my bird. Scanning the sky I found it ( so I thought ) WTF! It wasn't responding to the sticks. Put it in RTH and it starting flying away. Holy [EXPLETIVE REMOVED]! I'm in trouble. Switched to home and angle but the quad still wouldn't respond. RTH again and it started descending 150' from my position. I ran along the fence line and peered around the corner. Another pilot was landing his drone, which btw, had the same profile as the Typhoon. ( longer arms ) I ran back to my original position and guess what I heard buzzing overhead. I had been spying the wrong bird all along! Bottom line, I panicked when my visual wasn't right and although I think I checked distance on the transmitter(RTH), I guess in my panic I didn't. I don't know anything about frequencies. Could the other pilot have affected my drone in any way? Add this to the Pre-Flight Checklist!