It takes time to get MRI results back. Lydia was able to distract Stiles for a day or two, since when she wasn't around to take his mind off of it, work did the job for them. They both had surgeries and patients to handle and shifts in the ER.

(The rumor going around that Lydia had made a swap monkey deal so she could take that day off with Stiles was totally false. Totally.)

But now it's the end of a shift and she's in the locker room putting on her street clothes as she glances at the door, waiting for Stiles to come through with news of his results.