Is there something under there he wants?
Might be the slight gap between the foundations. Try placing him centered on one of them.
You may be too serious, my friend 
I have found it and been able to place walls between the foundations. So it is there, just not in the visuals.
I would suggest he was perhaps an orphan raised by a family of ostriches, yet your pet pen probably had something to do with it…
Were you cruel to him when he was growing up? Called him names? Said he was a poisonous influence on the other pets? Told him he’d never be able to spin a decent web before he’d even tried?
I think she’s looking for her friend Wilbur. 