Has anyone seen the film teenage dirtbag? if you havent please could you have a watch or if you have can you try to answer me this.

The whole point of the movie was to show us how anyone-no matter who they are-can come into our lives at any moment, and impact us so greatly that we can't forget them.
Whether or not Thayer is dead, is left for the viewer to decide. At one point, he talks about how easily he could fake his death and no one would know, so that is a possibility, but it is also said that a body was found. It could have been his father or brother. Either way, its up to you.
As for the bathroom scene...Thayer tells Amber that its a "misrepresentation". He is talking about how Amber thinks that everything has changed since highschool, but Thayer knows that it hasn't. Hence...why he counts to five. He's showing Amber how quickly those feelings can come back and how nothing really changed.
Hope I helped and that wasn't too confusing! :D

I love this movie it is my fav ever