This movie is about a woman who gets hit with painters scaffolling and they think she is a missing heiress kidnapped at childhood. They take her to a mansion and they tell her she has to identify her favorate doll. By logical reasoning she picks the right one.

Give it a go, haven't seen it since the 60's.
Nightwing

Wow. Didn't think I'd ever find this one, but the good folks at TCM.com had figuredit out for us. The movie in question is Slightly Dangerous from 1943, starring Lana Turner, Robert "Marcus Welby" Young, and Walter Brennan. A reviewer at imdb.com summarizes the plot thusly: "Her problems start when she is hit by a bucket of paint in front of one of the daily newspapers. Since her clothes are ruined, and has no proof of identity, the people around her believe she has suffered a temporary memory loss. Thus begins her adventure in the big city in which she pretends to be the lost daughter of a millionaire."