Whoopsie wave describes the situation when you wave to someone you know and another person intercepts your wave mistakenly as if you are waving to them, e.g. caught in the crossfire of your wave.
I was waving to Eddy at the show and Phil thought I was waving to him. Awkward... Phil waved back to me as he was caught in a whoopsie wave. It's almost as bad as when Jim invited me to lunch, thinking I was Tony because his phone contacts were screwed up resulting in Jim texting me with an invite.