Nathan had cuts in the previous episode and now they're gone this episode when it is only one day after his accident evidenced by the hooker Derek beat up the night of Lupe Fiasco's concert at TRIC where he stole Peyton's jacket where she ended up in the hospital the next morning.
Peyton realizes there is something wrong with Derek when she sees the double y in an instant message she got and the email Derek sent with a picture of her. However, the subject of the email has her name Peyton in it, and it is spelled correctly. (The email address has it correct also, but it would have to be correct in order for it to be sent to her.)