M.A.,
Stress can cause a delay in one's cycle. If the body is under physical and/or psychological stress...then the reproductive system takes a backseat to other more crucial functions.
Your travel and disruption in sleep and routine could have just added to the issue.
Still, if you've still not started in a week, I would consider going to your OBGYN again for another blood test.
Try doing some consistent coping skills the next few days to decompress.
Peace and progress,
S.C.