Visible crew/equipment: After the beginning of the movie where there is an aerial shot of New York City just before we see Patrick getting at his office, the filming helicopter can be briefly seen reflected on one of the buildings' glass on the left side of the screen while it films the scene. (00:07:13)
Continuity mistake: When Bryce pulls out Paul Allen's card to show it to Patrick, he holds it in different ways between shots. (00:19:44)
Answer: There are two possible answers. First, Carnes doesn't recognize Christian Bale as Bateman, instead thinking he is someone named Davis. He insults Bateman and thinks "Davis" left the message as a joke. Realize also that someone claims to have seen Owen/Allen in London, but mistook Herbert Ainsworth for him. Second, Bateman is delusional and only thinks he killed Owen/Allen, who is in fact alive and in London.
Greg Dwyer