He couldn't help but be disappointed by Suki's absence. A knot formed in his stomach when he heard she wasn't around. She had been the first girl who he had kissed, and although he hadn't felt much at the time, Sokka had been eager to see her again. After Yue's death, he knew that Suki may be able to fill the void left in his heart.
She wasn't there, and though Sokka knew that he had a job to do, his head was clouded with disappointment the rest of the visit. Sokka had wanted to see her again and he had wanted to know if the warrior could take his mind off of Zuko.
A few months before, she hadn't been enough to distract him from his thoughts about Zuko, but now, now that Yue had done it, Sokka was sure that Suki could be the one. Suki would have been able to make the thoughts disappear. They could have been happy, and she could have changed him. But, she was gone and the thoughts of the Firebender lingered.