The Collaborative International Dictionary of English v.0.48:

Unastonished \Unastonished\
   See astonished.

Moby Thesaurus II by Grady Ward, 1.0:

20 Moby Thesaurus words for "unastonished":
   aweless, calm, composed, cool, expected, expecting, inexcitable,
   unamazed, unastounded, unawed, unbewildered, undazed, undazzled,
   undumbfounded, unimpressed, unmarveling, unmoved, unsurprised,
   unwondering, wonderless