Staffy Phantom Pregnancy...?

So i got a Staffy, She's a year old and she's lovely, I took her to the vet for her Booster jabs, and general check up, and the vet says shes fine but she's having a phantom pregnancy, it has worried me becasue i havn't seen any of the signs you expect to see with it... the vet was in a hurry because it was like 6pm, is there anything i could have done to trigger this... she hasn't been spayed but she is booked in for a few weeks time. thanks