Is it "misheard" if you grow up hearing "thing" instead of "think," or is this evidence of language variety/change? Apparently both forms have existed side by side for over 100 years. Even if "thing" was a mistake in 1898, it strikes me as audacious to claim that teenagers growing up in Michigan in 2017 are making a mistake when they say it today.
According to the NPR discussion "most" Americans say "you've got another thing coming." Perhaps "think" is a shibboleth for some speakers of AE, but I question wheher the thing/think difference is (primarily?) regional.
We've been over this before. 'Thing' is widespread, but wrong.
hm--us apparently believes that "think" is the only correct version, the one that should be used by educated Americans. I would argue, however, that President Obama is a highly educated and eloquent speaker of AE. He uses "thing." So do I.
Apparently "another thing coming" has been around almost as long as "another think coming." Perhaps Americans in the Midwest, many with German heritage, were aware that carrying Auslautsverhärtung into English contributed to a German accent. Maybe they hypercorrected "think" to "thing," causing a reanalysis of the idiom. Personally, I see "another thing coming" as a subtle threat, whereas "another think coming" (which I was unaware of before coming across the earlier discussions in LEO) states simply that the person ought to reconsider. Whatever the origin of the idiom, "another thing coming" has been thriving in my part of the country for over a hundred years and is used by, in my opinion, everyone.
I understand that hm--us's concern is that people using LEO learn correct, standard English. Some people, like her, consider "another thing coming" to be a non-standard error, hence the tag "fälschl." Other people consider it a standard variation on an idiom, and they would find the current LEO entry accurate.
Good luck! Whatever marking LEO chooses will be disagreed with by some.