Tempted as I am by "hide" I have to say prep.
Go to every rehearsal (if the preschool will let you -- explain the situation to the teacher and I'm sure they will). Then sit in the same spot at every rehearsal and tell him you will sit iin that same spot at the performance. That might get him used to seeing you there and he will know exactly what to expect. (The only reason the teachers might say no is if they worry that other kids will ask "Why isn't my mom at the rehearsals" but you and the teacher can work out something where you are a "helper" those days or whatever.)
Also ask him to rehearse his songs for you at home daily.Don't press hard or make it a chore, just get him to sing them and be sure he sees your smiling face as he does so.
I think I recall your original post about this issue. Poor little guy. But as someone else noted, if the last time this happened was last Christmas at a program, he might have a totally different reaction this year.