Here's a line in action:
You're waiting for a train, eager to get home after a long day at work. As you sit on the platform listening to your music, a beautiful girl comes and sits down next to you.
What do you do... let the moment pass and watch her leave or take life by the balls and think of cringe-worthy line that will instantly grab her attention?
Of course you choose the second option.
Without thinking you take your headphones out, turn to her and say...
"Excuse me? Sorry to bother you, but I can't seem to find... dammit... [look down confused for a second] I've lost your number, can you give it to me?"
When your words sink in, her initial look of shock wears off, you can follow up with:
"Here you go, just pop it in there" [Hand her your phone].
The level of confidence you need to pull this off is HUGE. If you decide to use a line like this, practice it in the mirror a few times before so you can get your routine down.
Warning: If you screw it up, you'll look like a weirdo and using it on a train platform like this example, runs the risk of you seeing the same girl again. Epic embarrassment.