Your father should ask the solicitor for a breakdown of the fees from the VHI for this, including the dates the supposed treatment occurred. At the same time, he should check with VHI if they have any record of lodging this claim, and if they do, what it refers to.
Regarding the substance of your topic, I think you might get a better response in another sub forum. My reading of this is that your query isn't specifically to do with the VHI, but more about what the solicitor said and what the solicitor did.