pastel of baby girl

this is a drawing of a baby girl's head about 2 or 3 years old with short curly hair. she has fat cheeks and is looking down and to the left. It is done in dark pencil and accented in black ink and her cheeks, lips and beaded or pearl necklace is pink pastel. The signature is faded but may be R.B.S. in fancy letters in the lower right corner. About a years after I bought it I found a print of it in an art store. The owner couldn't give me any information on who the artist was other than he thought it was from a master. To me it does not look like the style of a master but more modern.