Can a Dr tell if you were pregnant after miscarriage at only a few weeks?

My sister took a pregnancy test just a couple days ago and it said positive, when she went to take another one (because she wanted to use the new tests that tell you how far along you are) it came up negative and so bought a couple more and they were negative too. If she goes to the Dr and she has miscarried will he be able to tell that she was pregnant at all in the first place?