The point you were making is that the ammonite stone wasn't necessarily "chosen" by the builders and you pointed out that lots of modern visitors miss it when they visit. My point was that it is more likely than not that the builders were aware of the fossil when they chose that particular stone to go in that particular monument. Based on the fact that they were people who were used to examining stone for its textures and properties, it's highly unlikely that they didn't notice it.
I wasn't suggesting prehistoric people were better, or superior, but I am suggesting that they were familiar with their chosen materials. Taking out the ancient people v modern people aspect, if I build a house, I'll be aware of the particular bricks I use to build the walls. But when people come to my house, it's not certain that they will notice. So a visting TMA-er not noticing the ammonite stone isn't really either here or there as to whether the stone was chosen by the builders. :)