I can't directly answer your question, but the reason that adding the
event listener to the hidden button on document ready does not work is
this (or at least this is what the library I was working with did):
When the Thickbox loads, it does not "directly" reference the
container it's loading. It takes the HTML from the container and
basically cut/pastes it (document -> thickbox).
When you close the Thickbox it cut/pastes in the other direction
(thickbox -> document).
By doing so, its eliminating any events you're adding to the elements
initially.
I can't remember if you can even access the elements using the
standard $('element'). syntax once they are inside Thickbox.
If not, you could use the livequery plugin (http://docs.jquery.com/
Plugins/livequery).
