If Char bothered to look over his shoulder to gauge a reaction from the ghost, he would have seen her stare at the note for a few moments in total shock, before a grin split her face.
No, it wasn't romantic, it wasn't poetic, but it was so very Char. And Nyx was perfectly happy with that.
She didn't bother trying to catch up to him- never mind just how much she wanted to hug him. He'd had his reasons for running off, and she wasn't going to disrupt them.
So, Nyx went through the rest of the day with the note in her pocket, and a silly grin plastered on her face.
She did leave a similar note under his door later on, knocking on the door to get his attention before hiding in the shadows like a creeper. The note said simply "Thank you."