That's pretty weird. There's two bridges in Eldin Province:
Warped-out bridge - north Eldin
Broken bridge - east Eldin
The Bridge of Eldin is the one in the north, and a huge chunk was warped out when you traveled to Lanayru Province (the portal appeared above it at the same time). If there's no portal there now...I dunno. You don't have to fix it to beat the game though.
In fact, there's only two disadvantages to not fixing it: you can't get an orange Rupee later (before the City in the Sky), and it just makes it a bit harder to travel