High Strangeness In The Store

Had an interesting experience last Thursday,  I am a driver for a visually impaired friend, we went to a health food store in town, there were very few people in there, my friend had everything she needed and was about to check out, there was someone ahead of her so it was going to be a few minutes before it was her turn, so I decided to go back a few aisles and look around for a minute. There wasn't anyone near me, as I walked I was punched in my left shoulder, it wasn't a violent act, but it was harder than just a mere muscle twitch. I turned around fully expecting to see someone standing there, perhaps someone I knew or perhaps someone accidentally ran into me and was about to say "excuse me" or "sorry".  There was no one there, there was NO ONE there, I turned all the way around, I even said "what?" out loud, sometimes I get an answer, but there was no response. I don't know who or what that was, I just know it happened.

I didn't feel anything in particular (other than the shoulder punch), I didn't detect anyone or anything, but someone or something was definitely there, not sure what they or it wanted, that was as far as it went.

I have had strangeness happen in stores before, I have walked down a long aisle, all by myself, on concrete floors, and had things like boxed cereal begin to fall, one by one as I passed, maybe a few feet further, I have had to tell whatever it is to stop it, then I went back and picked up the boxes, it has happened on several occasions to me, fortunately it hasn't happened in a long time.