Wow a fortnight! That is restraint! When Bella was expecting our litter of pups I was getting phone calls from all of the potential new puppy owners day and night at all hours, from a few weeks after mating right up until the birth and beyond.... I didn't mind a bit as I was also very excited about the arrival of the pups and it was great to know that all of the puppy owners were so keen and committed to the pups and Bella.
So do give them a ring, ask how the bitch is doing health wise etc.. etc.. and just tell them how excited you are etc...
It'll be reassuring for them to know that you're still 100% sure you want a pup from them and are sticking to this particular litter, even though the vet scan has thrown doubt over the possibility of pups.
Good luck, fingers crossed for all concerned
Mary xxx