I messed up early on and didn't get that far. Was there a tile on hand then that could connect to the stood on one after everything else is removed?
before I reach I usually always try to shuffle the tiles so that I have options available later.
I think this particular time, I had 3 tiles (from Fibonacci) I placed a purple gem tile so it swapped out one of my options. I am guessing that when the boss jumps and all tiles are reshuffled, the people gem activated a second time and it swapped out the other tile as well...