Hello-
I had the same problem in 2006, I was abroad and had to begin the visa process. I think it depends on your Consulate, in my case the Houston consulate allowed my mother to drop off all the required documents with a photocopy of my passport and a signed statement from me saying that I gave permission to my mother to drop off the documents on my behalf.
Once you get back to the US then you personally have to go to the Consulate with your passport and they will apply the visa. I can't remember if I got it back in the same day, which is what I think happened, or had to wait a few more days.
Hopefully Miami works the same.