[stale]

from personal experience with a lab breeder, the ultrasound seems to have about a 50% failure in terms of spotting pregnancy at 30 days. she always had it done, as a routine thing, but never trusted it.

and i'd say call your breeder, point out what was agreed to (a puppy from the just born litter) and ask for either a pup from this litter, or your money back.

if it turns out it's an honest mistake (don't think it's likely, but i'll give benefit of the doubt) all is fine. if not, study, and find yourself a reputable breeder. there still are some out there.