The Collaborative International Dictionary of English v.0.48:

Nonattendance \Non`at*tend"ance\, n.
   A failure to attend; omission of attendance; nonappearance.
   [1913 Webster]

WordNet (r) 3.0 (2006):

nonattendance
    n 1: the failure to attend [ant: attendance, attending]

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "nonattendance":
   AWOL, French leave, abscondence, absence, absence without leave,
   absentation, absenteeism, absenting, cut, day off, default,
   departure, disappearance, escape, excused absence, fleeing,
   furlough, holiday, hooky, leave, leave of absence, leaving,
   nonappearance, running away, sabbatical leave, sick leave, truancy,
   truantism, unexcused absence, vacation