AFAIK such thing doesn't exist. Two different protocols...
Since most of the others who posted on
this thread confirm what you say then this post in that thread must be wrong:
"You can use an external Firewire to USB video adapter for a laptop, just be sure it is made for that purpose. I use the Pinnacle Moviebox Ultimate unit and it works perfectly, even giving me camera control. You can use the captured video in any editing program, not just Pinnacle's."
Looks from
this video demo importing a signal via firewire to thunderbolt is also an option.
But both of these examples relate to converting video signal from a firewire output to a different type of laptop input. That does not mean software programs used to import photos can talk to cameras via this kind of link and that may be the straw that breaks the camels back?