On Forgetting To Remember

The thing about forgetfulness is that

A creature that someone believes you know

Has left the rocky perch where once it sat

And wandered off to where such creatures go;

That when you are reminded that it lives,

You saunter through the forest in your head

And though you spy its friends and relatives,

You fail to see it rested on its bed,

Then snap, and swear that creature never was,

You pick a fight with all who disagree,

But not one proof suffices you because 

A thing that cannot be can't also be

Till one day as you step in for a walk,

You chance upon it stretching on its rock.