The Collaborative International Dictionary of English v.0.48:

Unsuspicious \Unsuspicious\
   See suspicious.

WordNet (r) 3.0 (2006):

unsuspicious
    adj 1: not suspicious; "deceiving the unsuspecting public" [syn:
           unsuspecting, unsuspicious]

Moby Thesaurus II by Grady Ward, 1.0:

52 Moby Thesaurus words for "unsuspicious":
   artless, bluff, blunt, born yesterday, candid, childlike,
   confiding, credulous, dependent, depending, direct, doting,
   easily taken in, easy of belief, fond, frank, guileless,
   inclined to believe, infatuated, ingenu, ingenuous, innocent,
   naive, open, openhearted, outspoken, overconfiding, overcredulous,
   overtrustful, overtrusting, plain, reliant, relying, simple,
   simplehearted, simpleminded, sincere, single-hearted,
   single-minded, superstitious, trustful, trusting, trusty,
   uncritical, undoubting, unguarded, unreserved, unskeptical,
   unsophisticated, unsuspecting, unwary, without suspicion