If I go to a new doctor and tell him I've used to have a prescription for Concerta, will he know if I haven't?

I haven't been diagnosed with ADD but know that having a prescription for Vyvanse will greatly help me in school, I know my limits and would not abuse such a prescription. However, I know that doctors are wary about writing ADD medicine prescriptions to college students. If I tell a doctor that I've previously had a prescription and needed to switch doctors due to insurance and need a different medicine, would he somehow be able to tell if I was telling the truth? Please, no moral lectures, just straight answers. Thank you.