I believe you should qualify for PR.
First, the fact that your mother worked in Ireland and lived there with your father and you, means that when she returned to the UK she (and her family) could make use of the EEA regulations (this is referred to a "Surinder Singh" route after a case law by this name). So the solicitor was wrong is saying your Residence Card was given by error.
Second, there are several provisions in the EEA Regulations for cases when the EEA national dieds. I believe you probably could meet the requirements for at least one of them if not two:
- According to regulation
15(1)(e), if the EEA national was a worker and died and has been living in the UK for two years before his death and his family member has been living with him, the family member qualifies for PR without the need to complete 5 years.
You didn't tell us of your mother was working in the UK or not but as she worked in Ireland and was a returning citizen, she should have kept her worker status even if she did not work in the UK. This means that you have probably have obtained PR in 2006. It is not clear why the judge in your appeal didn't order the HO to confirm your PR. that's why it would be useful to get hold of the appeal papers.
- According to Regulation
10(2), a family member of EEA national who died and lived in the UK for at least a year, has retained his rights of residence which allows him to live and work in the UK. This means that from 2006, you and your father have retained your rights. In order to qualify for PR, your (or your father) work would count for PR. if your father worked continuously from 2006-2009 and you were dependant on him (or living in his house when not in school), then you would have obtained PR in 2009.
Your case is not a standard case the HO sees everyday. I suggest you read the regulations and the HO caseworker instructions (
here) to understand the requirements. I suggest you attach a cover letter to the application explaining why you believe you have achieved PR already (probably in 2006 and if not, probably in 2009). I would also try to get hold of the appeal papers.
The solicitor you talked to doesn't seem to be familiar with EU regulations. I would probably look for someone who is more knowledgable or apply alone (the application is free).