I've noticed a bug in org-mode's LaTeX exporting of footnotes when a buffer is narrowed to a particular section. To reproduce, try to export the following org-file to a LaTeX document, and inspect the resulting LaTeX code -- it will have stripped the math environment off of "\tau_s":
* Test Section Here we test whether the footnote is exported correctly [1]. Be sure to narrow the buffer to this section only before doing a LaTeX export. * Footnotes [1] $\tau_s$ is blah blah blah. Let me know if there's a workaround for this (apart from just "don't narrow the buffer"). Thanks! Regards, Mark