you have two choices.... go back to photoshop and use the magic wand to select the transparent area... then go to select---->inverse. Then go to your paths and select "make work path" and enter .5 in the next dialogue box. Save your path and resave the file. Now when you import into Illy, that path will also import. BUT... it is probably a little jaggy from the magic wand...
You can then either use the smooth or simplify tools to fix the path in Illustrator. Or... sometimes its easier just to draw the path in AI by hand to begin with.
S