We don’t know if Regina saw him before as an adult.
Regina: I need you to look into something, Sheriff. Someone’s in town – someone new.
Emma: Yeah, I know. I gave him directions to Granny’s the other night.
Regina: You talked to him? What’d he say?
Emma: He asked for directions. What’s the big deal? Who is he?
Regina: I don’t know. I asked around, but no one seems to know anything. There’s something about him. Something familiar.
Emma: He must be one of the untold millions you cursed.
Regina: What?
Emma: Oh, you know. The curse. Henry’s whole thing.
Regina: Sheriff, I need you to find out who he is, what he wants and what he’s doing here.
I find that pretty ambiguous about whether she had seen August in storybrooke, or was thinking of little boy Pinnochio all grown up. She also says to Greg/Owen that she almost didn’t recognize him–but she eventually does. So she can place a grown up face to a little boy’s face–but perhaps August was a little harder for her to recognize as she hadn’t spent as much time with little Pino as she had little Owen.
“If I had a world of my own, everything would be nonsense. Nothing would be what it is, because everything would be what it isn't. And contrary wise, what is, it wouldn't be. And what it wouldn't be, it would. You see?” -- Lewis Carroll, Alice's Adventures in Wonderland & Through the Looking-Glass