In at least 99999 out of a hundred thousand "submittal spamming" cases, you find out what happened by asking the webmaster what he did.
For the other case, you don't worry about it, and instead you worry about something that's more likely to happen -- such as a drunk driver bashing you off of the freeway, a natural disaster (fire, flood, tornado, hurricane, lightning), or your ISP being shut down by lawyers.
There's no standard mechanism for this problem, and there won't be, because the problem is just too rare to know what mechanism would be effective. It's just one of those odd situations that "humans just take care of" when they notice.