If this were the case then I'd see ghosts all the time, considering I work and have worked in numerous places after hours and on my own, including hospitals and various old hospital wings under-construction, yet have seen absolutely sod-all.
Most people who see ghosts are either intentionally looking for them, and thus see them around every corner (same with UFO hunters, Bigfoot hunters and everything in between) or are simply mistaken, drunk, or under some type of mental strain.
The amount of supposedly haunted buildings I've been in at night, on my own, and have never seen so much as a bloody orb. Heard lots of things, same as I have in my own house at night when it's settling down, nothing supernatural, just average noises that ghost hunters would assume came from some spirit, because that's what ghost hunters do.
Outdoorsmen see prints in the mud; it's an animal. Bigfooters see prints; it's a Bigfoot. UFO hunters see an alien craft, normal sods see a weather balloon. And so it goes. On and on.
This "spooky feeling" is essentially a load of nonsense, and is just a person's natural unease in an empty yet otherwise harmless building, and is brought about via ghost stories and Horror movies, and a real-life awareness of general weirdos and murderers being out there.
People think about ghosts way too much, no wonder they're seeing them in every other nook and cranny of old, abandoned buildings.