Nope. Not phantoms. Good try though.
The main character is for certain a man and he's recently unattached. There is a big scene in the back of the storeroom of the supermarket. It's really dark so they're using flashlights. A couple of the "dunderheads" (they have them every book) are trying to escape out the back loading dock. They get the door halfway up when the big confrontation between the dunderheads and our hero's group (in which I remember an old man) the flashlights get lost; the fog starts creeping in; and before they get the door closed tentacles (I'm pretty sure) come through the bottom, kill some folks, and drag the head dunderhead under the loading dock door kicking and screaming. It's a dangerous mist.....there are lots of things in it.....no one sees anything in particular, but there are lots of strange noises....and of course the tentacles.
This is driving me crazy.
I also think at the end when they travel back in time they drive under a brontosaurus or something like that....then the story ends.
I know so much about the story, but can't find a name or even a mental picture of the book....this is driving me batshit
As for the Koontz connection
I've only read a handful of Dean Koontz novels. (I really don't like the way he ends his stuff) I coincidentally still have them and have looked through them all to no avail.
I'm about 70% sure it was a Stephen King thing....but then again I've no idea what I'm talking about