Sounds like the evidence image was provided on a CD? Meaning it could never have been a full disk image unless it was a circa 1990 4GB drive or an encase EWF format image? which is very very unlikely.
Unless they actually cut/copied the image from the original pc then put it on a CD and handed it in? then couldnt find it on the original machine? in which case wasnt a bit-for-bit clone taken at the time of seizure? uhm, what about using encase/ftk to recover? or are they actually working from a live machine? non-writeblocked?
Not enough info here, sounds innacurate/moronic to say the least.