Seems like the best way to conduct oneself in this scenario is to be absent from it.
Failing that (after all, we none of us are immune to necessity...I'll say no more), try lurching out of the store and screeching randomly at the sky. Claw at the air in front of you and cry out for your flowery bonnet. Finally, be sure to meow passionately at anyone you pass.
Sounds nuts, but it works for me. I don't take kindly to strangers approaching me in the dark, especially in the depths of Wal Mart.