Random Question...

Last night I was watching the episode where David plays his guitar during the training, and Tim quits (sorry, i forget the exact episode).

But I noticed something. Tim was sitting beside Dawn (reading the paper or something) when Donna was talking to her, saying she'd "find her another bloke".
Dawn said she hadn't split up with Lee.

But when Tim comes back in and asks her out for a drink, he says that he "knows she split up with Lee".

I was just wondering if I was missing something, or if Tim didn't hear or something.... :S