i learned about pet stores after i got snickers (i hear this is usually the case) i would have your new little one checked out by your own vet even if the cough is better... most pet stores have a health guarentee that is only honored if you have the pup checked out w/in a certain amt of days from leaving the pet store
also if you have all the akc paperwork then you have the breeders location etc... check the state...
and finally i would do a pet shop puppy report and find out more about where she REALLY came from not what the pet store told you
CONGRATS on your ltte one and good luck and post pics as soon as you can... hope he/she is feeling better soon!