Try downloading RDBRecov from Aminet, unarc it, and try to run it. It will give you valuable information, and it will also give you the answer to your question.
Read the docs carefully and do as prompted. If you fail to do so, you will most likely lose your data, but if you do as stated, then there should be a good chance that you might salvage your data. I know I did when I lost my RDB.