I used to work in a sawmill/pallet factory. Most days I worked alone in a metal building, just cutting the notches in 2x4s that let fork lifts pick them up from the side. I liked it as I didn't have to deal with anyone and could listen to audiobooks and the radio all day. There maybe eight people what worked at this factory, including myself.
One day as I was stacking my completed boards, I looked up and saw four men in expensive suits standing shoulder to shoulder watching me. Three of them were older, late sixties to early seventies, and the one on my right looked to be closer to my age, so early-to-mid twenties. One of them leaned over and began speaking to another, but none of the four ever took their eyes off me. I didn't know what they were there for, they weren't holding clipboards or anything, and their suits were much too nice to be wearing in a shop full of sawdust.
I reached over and turned off the notching machine, then took off my hearing protection/headphones, and asked, "may I help you gentlemen?"
As I stepped toward them, they all four turned to their left, and silently walked single-file out the door.
Later I asked my boss who those guys were, and he and my co-workers all claimed they never saw them, and began making fun of me and accusing me of hallucinating and/or taking something.