The Collaborative International Dictionary of English v.0.48:

Unobserving \Unobserving\
   See observing.

Moby Thesaurus II by Grady Ward, 1.0:

47 Moby Thesaurus words for "unobserving":
   ableptical, amaurotic, benighted, bereft of light, blind, careless,
   color-blind, dark, dim-sighted, disregardant, disregardful,
   distracted, distrait, eyeless, heedless, hemeralopic, in darkness,
   inadvertent, inattentive, incurious, indifferent, inobservant,
   mind-blind, negligent, nyctalopic, rayless, regardless, sightless,
   spiritually blind, stark blind, stone-blind, thoughtless,
   undiscerning, unenlightened, unheedful, unheeding, unmarking,
   unmindful, unnoticing, unnoting, unobservant, unperceiving,
   unreachable, unremarking, unseeing, unwatchful, visionless