Well, without knowing any personals I can give you my advice.
My husband and I have been apart a few times. The first time was in highschool (yeah, we're highschool sweeties) and I left him with a necklace I really loved. He gave me his highschool ring. The second time was after we lived together and he did his study abroad in Hokkaido, Japan. I gave him Siggy, a stuffed penguin I've had my whole life. That little puff ball was the first thing that was given to me, actually. He left me with his stuffed wombat creatively name "wombat". Siggy and Joe came home safe and sound, though Sig's squeaker is a little worse for wear. The third time was when he moved here to Osaka and I was finishing my thesis back home. He left me with his favorite sweater and I sent mine with him. Like Sunderland said, I always go for something that means something. Even those sweaters shared a special meaning for us.
Since you said you may be doomed (I certainly hope not, obviously) I would say don't send your version of Siggy. It would have killed me in some small way to lose that as it was a gift from my grandfather and aside from my name the first thing I ever got. But, if you have a favorite sweater or something like that that your girl likes, that may be a good choice.
I always go for sentimental gifts. I know guys aren't supposed to be sentimental by some weird standard, but every guy I know is.
Other than that is there anything she really likes? I'm a penguin lover and my partner is a duck lover. I can send him a picture of a duck and it makes his day. I've gotten him stuffed ducks and duck themed ties and he loves them. It's a good bet to find something like that to give her.