R1. B2 hits a deep ball to Left Center Field. R1 tags up after the catch and advances safely to 2B. (He is now the winning run in scoring positon.)
Ball still in play, and the DM yells at F4 (who is retrieving the ball from F8) to throw to first base. He throws to F3 who steps on the bag. That's it! No discussion! No claim that R1 left early.
I would suggest that everybody in that ball park knew what was going on, but how "unmistakable" were the actions of the defense to constitute of legal appeal?
What criteria do you use that make an appeal legit?
I wouldn't have ruled on your play right away. It's just not that "clear and unmistakable" to me.
The only appeals where I wouldn't need a verbal request is when it is obvious that a runner failed to tag up properly on a caught fly ball (e.g., he's already at the next base when the ball is caught, he's trying to high-tail it back to the base before the throw gets there, etc.) When it's a case where the runner left the base just as the ball is caught, they need to tell me what they're doing.
There is always the umpire quiz question that asks what's the max number of appeals possible on a play? The answer is 10: Bases loaded, and B4 homers. An appeal is distinctly possible at every possible base that any runner could have touched/missed. In one of those, I would expect the defense to correctly and unambiguously tell me which runner was in violation at which base.
Back to the OP......Since there was only one runner, I definitely could see your point in that he's the only one who could have violated any running rule, and the only possible location was at 1B. In the context of the play, it was an appeal, and the alledged violator was unmistakably evident, although the defense never said a word.
Even if you and everyone in the park knows it's an appeal?
R2 - leads off - line drive caught by F6 in flight - F6 throws to F4 on 2B before R2 gets back. You require a verbal? If so why?
It's situational. Sometimes there's only one reason the defense is doing what they're doing. Plus, you're going to hear directions from the dugout, so you know what's going on. No need for an 11 year to try to stumble through verbalizing it, if you can avoid it.
Other times, like a missed plate on a grand slam, you're going to need to be asked the right question.
In the OP, the defense would have been wise just throw it to second, and tag the runner to make the appeal, instead of tossing it over to first. But again, that's just bad coaching.