do guys lost interest in a girl they had an intimate moment with?

Depends upon how bad/awkward the intimate moment was. Most guys would rather forget about the really terrible ones. Those are the ones which "were a mistake."

Sometimes. There are a lot of variables but that's pretty much what happens with a lot of hookups - unless there is a tremendous connection and both people really want a relationship.

If two people have sex too soon after meeting each other, then the chances of this happening are greatly increased.

Some times, they're usually the crappy ones anyway