I was a relatively early adopter to Facebook, though not Harvard- or Ivy League-early. It didn't have a hot-or-not style rating at that time. Poking was a feature, but I'm not sure it was ever that popular.
But I have a feeling you are confusing things and timelines. Perhaps you are remembering the actual hot or not site that did just what you remember while thinking of the facemash or whatever that Zuckerberg made prior to FB that we probably all learned about when we watched The Social Network.