I imagine your clothing acted as a baffle. Baffling microphone is a way to block out extraneous noise (usually from the sides)... I think the "Blumlein" mic placement method uses a baffle, but I'm probably mistaken on the name...
However, your method of baffling covers the mic too, it reduces ALL sounds recorded, but as in your case, the music is loud enough that it is not effected very much... Lucky I guess, cause I have some stealth recordings from "under-collar" and "inside hat" that are way too muffled to be really enjoyable...
I'm wondering about using a concave sound reflective "satellite dish" type attachment to focus sound on the diaphram of a mic. Pointing a card mic into to "dish", facing backward to the stage...
But I have no idea, I've only been a taper for a month or so!
Good luck! And "sweeeet..." on the Euro Tour and street recordings!
Terry