Word for the inability to do simple things when you don't look at it

"word for the inability..." suggests you are looking for a noun, not an adjective. I'd go for"clumsiness", or "awkwardness"

clumsy - adj. "awkward in handling things" ODO, "lacking dexterity" Merriam-Webster

or, as has been suggested in a comment by @Oldcat, "normal" (adj), if you consider that there are a lot of people who find it difficult to perform tasks with their hands without looking at what they are doing.

The verb that comes to mind in decribing the action you are referring to is:

To grope:

• to search for something by reaching or touching usually with your fingers in an awkward way.

  • I groped for the light switch.
  • She groped around in her purse, looking for her comb.

also to struggle may be useful to describe the action:

• to try to move yourself, an object, etc., by making a lot of effort in the end

I struggled to reach the plug under the table without bendind, but in the end I had to stoop down to put the plug in.