I was at right place and the pillars were around the rim of the pit. I didnt need any additional seeds though I had used all in crafting already, but the 2nd Heart of Star was spent at last stage for the choice. I guess it was just late last night...
You're not the first to miss it, trust me.

I think because everything is so monochrome (other than dashes of red) in the Atlas stations, the pillars are so easy to miss.