Absolutely the Vyvanse you took, if you were taking it on a regular basis, should show up on a blood test IF the test was correctly ordered. A regular blood panel for amphetamine might not show Vyvance because it does not check for that particular metabolite of amphetamine. A therapeutic blood test for Vyvanse, however, would show its presence in your system.
Humans are not perfect and its possible that the lab made an error. If you can ask to have the test redone and make certain which test was being done (general test for amphetamine vs specific to Vyvanse) it would be helpful.
Here is what a normal Amphetamine blood panel tests for: http://www.nmslabs.com/tests/Amphetamines-Panel--Blood/8600B
You will see the chemical derivative name for Vyvanse is not there (lisdexamfetamine).
This is the test for Vyvanse: http://www.mnslabs.com/tests/Lisdexamfetamine-as-Metabolite--Blood/2800B
I would ask your doctor to retake the blood test, which seems reasonable if he is willing to check a saliva test which would be at a later date.
I hope that helps,
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