Non-lawyer but…

If a jury comes to a conclusion then the defendant is not guilty then it’s game over. A mistrial had to be called before deliberation happen, and that would have to have some material misconduct during the trial, not just ‘I think we gonna lose’. A guilty verdict could be appealed but that appeal is only to decide if the case was conducted fairly (for a retrial request) or to assess the validity of a sentence.

Basing it off some time I did a lot of legal/court adjacent work for a few years, but I’m pretty sure that’s right.