That is exactly what happened to me too. Customs or the fda stuck a little piece of paper in my original package telling me that my meds were detained. Then a couple of follow up letters that were a bit more formal. They looked like IRS letters except they were customs. This was the only time I ever had meds detained.
The company was suppose to resend and pretty much folded so I was out money and meds which I hate. Very aggrevating.