I've never seen anything directly, but after losing the most important person in my life suddenly and tragically, I did see many many odd things that were directly related to her at strange times in the following months. It could be said that there was an increased hypersensitivity for all things related to her, but some were just far too random for me to ignore.
I'll admit that it is hard to buy a lot of ghost stories, but the arrogance of declaring something as complete nonsense because you do not have a logical explanation for it is unfortunate. History has shown that "common sense" isn't always the way to go. The world turned out not to be flat, right?
I have no logical explanation for disco, yet that was all too real.