Details matter. Did you see the daggerboard? Was it wood or metal? Was it clear panels or was it actual holes? Some of the dinghies I sail have open holes on either side of the transom and the center is solid. Later models of the same dinghy have solid transoms.
Was the hull rounded or did it have hard chines (edges) to it? That can help a lot in dating a design as many one design dinghies originate from the 1920s onward and hard chined hulls are typical of that era. Snipe, Lightning, Comet, Star to name a few. Although I can tell you the boat you saw is definitely not a Star.