Unity - iOS Game Center - *Reliable* Highscore Submission

When I submit my score to the iOS Game Center leaderboards, e.g. a player recently beat their highscore with a score of 8, I want to submit that score to the Game Center leaderboards.

I do that, and all seems good so far. But, what if the Internet was down, or something when that happens?

Thus, is there a callback function when submitting the user's score that tells me if submitting the score was successful? I want to ensure the highscore is submitted properly.

A hacky solution to ensure the user's highscore is in the Game Center leaderboard is to periodically submit the highscore to the Game Center - maybe every time the user visits the main menu or once every day. Is this hacky solution the most reasonable and suitable way?