Thorin might not hate the Elf, but there was still a past there that would be hard to ignore. Of course, Thorin would keep the peace as much as possible for Bilbo's sake, but he also wasn't likely to seek out Legolas on his own either. After all, it wasn't in the nature of a Dwarf to be forgiving. But this particular Dwarf had changed quite a bit, so there was still hope of him coming around in the future and being even more friendly.
When Thorin had received the message from Bilbo about him being late, it kind of backfired. It only made him worry that something might have happened at work and Bilbo was upset or trying to handle it on his own. So, the entire time he had been waiting on Bilbo to arrive home, he had been trying to occupy his mind and not think about all the things that could have gone wrong.
In the end, this led to the dwarf sitting on their back porch and staring off into the distance. This was why he hadn't heard the knock or the sound of the door opening. He still sat right in his spot, hoping that once Bilbo did return home, he would be able to find him there.