I have activated a Merlin Trial in between two small bandit camps and there is a Fwooper den just over the hill. I have found and repaired two of the statues that are needed but I can’t find the third one. I have been looking up and down the hill in the area and i can’t find anything.
I had the same issue and found a YouTube video solving it (It is number 6). It was completely invisible to me and someone in the comments wrote the same. I just went to the location and Reparo’d an invisible statue.
I’m assuming you saw the one in front of you on the cliff to the right. Another one is behind you at the far end of the camp and the last one is almost beside to you when you’re stood on the trial circle hidden behind some shrubbery covering the stone that you can burn away (glows blue with Revelio)
You guys just saved me so much time lol. I reparo’d an invisible statue too. The third one Jod mentioned.