Leo was battling a monster with Percy and Annabeth, when he noticed something the others didn't. You, a little kid, were hiding behind a bush. And of my gods was he excited

You saw it? The Mist was supposed to hide monsters from you mortals. Unless.. you're not mortal. Which is exactly what was going on.

When the battle is over, he runs over and picks you up, soothing you in his arms. Annabeth raises her eyebrows, and says, "Really, Leo? No, we're not taking care of it." Percy just looked at Leo, silently cheering him on. Annabeth elbowed Percy in the ribs. "Don't encourage him..." Annabeth whispered to her boyfriend.

Leo grinned. "I'll take care of the kid! Please Annabeth??" He lifts you up in the air, spinning you. Like he found a new species, honestly he looked more of a kid than you.