It’s interesting and got me smiling. If I do a show on bass then the whole audience will be watching me and would certainly notice if I wasn’t there, as I tend to play solo shows now 😁.
To be totally honest I don’t think the average person really takes any notice of anyone in a band except for the singer or the drummer.
I did the most bizarre gig about 7 years ago. I was booked to play a New Year’s Eve gig at a club in Leicester. I asked if it was a reading gig or did he want me to learn a set; his reply was a bit odd “neither just turn up”. Anyway I kept in touch with him, a week or so beforehand I asked if he wanted a rehearsal, to which he said no, don’t worry, this is the easiest gig you’ll ever have to do.
Come the night I arrive and introduce myself, the drummer is setting up an electric kit, I unload my gear and set up. As we’re about to soundcheck he comes up and turns my volume right down, and signals me and the drummer to follow him backstage. There he let’s us into the secret. He usually plays as a duo with his wife using prerecorded tracks, the venue didn’t want that they wanted a band, we were just there to make up the numbers, essentially miming to the tracks. Nobody at all noticed.