It's unlikely that it was a false positive. False positives are extremely RARE. I think you should go see your doc and your hubby should have that sperm count checked.
False positives are rare.
Was it a blue dye test? If so, I'd recommend going and retesting with a pink dye such as FRER. (First Response) Blue dye tests are known to give false positives more than others and it's possible that it could be one, especially considering your circumstance.