The investigators report is one piece for the court to consider, it is given weight, but its not the final say. In addition, sometimes the investigators get it completely wrong. It sounds like you are doing this alone. You would be well advised to have an attorney argue this who knows conservatorship law.
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The judge can deny the petition for many reasons but most likely will not for an incomplete investigation.
Since your mother won't be present and the court investigator hasn't talked to her, the judge most likely will not grant your petition.
A likely outcome would be the appointment of counsel for your mother under probate code 1471. The matter will be continued and everyone will get to try again. (lather, rinse, repeat)