The best thing I would do is to corner her, but it will be very difficult. My friend had an outdoor bunny who would sometimes get out. When he did, they'd all get together and chase him around the backyard until one of them caught him. I don't really suggest doing that, as it takes a long time and is tireing (not to mention stressful for the rabbit), but it usually works.
Just leaving a carrot or a bowl of lettuce outside won't work all that well either. Why should he want to eat boring old lettuce when he's got an entire lawn to graze in? Maybe if you left out a favorite food, he would come. My rabbit has an obsession with bananas. She lives inside, but I know that if she got outside, just leaving a banana out would make her come. Really, I'd suggest getting a large peice of fabric, like a sheet or something, and trying to throw it over it, which should slow it down somewhat, and then picking it up.