A phantom limb. Feeling it although it is not physically there. The sensation is predominantly pain. For the love of it: does pain have any other color but red?
What is a facebook thumb then? A virtual limb once again. Created for the purpose of expressing/indicating a feeling. But there is only one: like. So this limb is pretty restricting. We could say it’s a one trick pony or, better, that it has a fixed idea. It’s monomaniac. Interested in nothing but the reproduction of like.
A phantom limb? More of a vampire limb, a zombie limb, a polyp limb, capable of multiplying itself. The undead limb.
So it is not really ‘you’ or ‘I’, dear Enrique, it is ‘it’. It likes it.