The Collaborative International Dictionary of English v.0.48:

Unheedful \Unheedful\
   See heedful.

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "unheedful":
   airy, careless, casual, cursory, degage, disregardant,
   disregardful, distracted, distrait, easygoing, flippant, forgetful,
   free and easy, heedless, inadvertent, inattentive, inconsiderate,
   incurious, indifferent, inobservant, insouciant, lazy, mindless,
   negligent, oblivious, offhand, perfunctory, reckless, regardless,
   respectless, tactless, thoughtless, unaccommodating, uncomplaisant,
   uncooperative, undiplomatic, unheeding, unhelpful, unmarking,
   unmindful, unnoticing, unnoting, unobliging, unobservant,
   unobserving, unprepared, unready, unremarking, unsolicitous,
   untactful, unthinking, unthoughtful