I don't find someone dropping off the grid for a day or two all that unusual. There have been instances where I've gone weeks or a couple of months without calling or texting people. Not that there was anything wrong, just that I had nothing to say. I'll admit I'm not normal and I can't recall anyone ever accusing me of being normal either, so take it as you will.
There is nothing wrong with just not contacting friends all that much, or not starting at the screen all day when you're sick. There is nothing wrong with any of that if there isn't someone expecting you.
But you should at least message your s/o "hey, I'm sick" at some point during the day. I don't say they should have a conversation, but a status heads-up is something you would expect in a relationship. If it's a one-time thing because you were so dead that you somehow did not wake up for 28 hours straight, then sure. But the nonchalance with which she came back in, after seeing the whole day of one-sided messages on her phone, feels a little disturbing to me.
That's why I think that there is something wrong - in a completely opposite direction to Hime, with Yoru. I'm getting flashbacks to "Koi no Zetsubou Koushin Kyoku", with how dissociated she seems.