Oh God, now I'm going to have to put in my DVD and watch it a third time just to look for this! I watched the second time with CC on the entire time, and I don't recall seeing any "I Love You's." As someone mentioned above, though, since it was just a faint whisper, it might not have even been captioned. Who knows.
I'll definitely have to watch for it, though. Through the whole movie, I kept waiting for them to profess their love to one another. They kept referring to their love as 'this thing' that grabs ahold of them, but they never once said to one another they they loved each other, and I wanted to hear it SO bad! So, I'll have to check it out.