faceplam
When you fail so hard your brain short-circuits and you start spelling 'facepalm' as 'faceplam' in your head like a lunatic.
'I failed the test so hard my brain started spelling faceplam instead of facepalm.'
'He failed his exam and his brain went crazy, spelling faceplam all over the paper.'
'She failed the quiz so bad her brain screamed faceplam at the top of her lungs.'