PJ's Sauron

[The Only Real Estel]

Also, you'd think that the eye of Sauron would have reacted to seeing Frodo, yeah so he didn't know WHY he was in Mordor but all the same you'd think he might assume as much.

Even if he didn't guess why the hobbit was in Mordor, he wouldn't have just let him be.
The lightbeam was ridiculous, but Sauron not acting on seeing Frodo was much worse. O wait, I forgot, Frodo eluded the eye by falling to the ground & blending in with the rocks .

(not to mention the fact that, even if Sauron would've somehow not seen him at first, that drunken dance he does before losing his balance would draw attention to him faster than you can say 'stupid')