Yes, if you all had not noted it, I would not have heard it. Now, yes, it is there. However, is this really a distinct word, or is it a kind of "sort of" word, like the contraction "n't" in English? By this I mean, could a couple of people actually carry on a brief exchange of "Mi?", "Musun?" . . .
It's fine, but it's kind of British, so Duolingo often doesn't have it until it's been reported a lot. As you can see, some English-speakers (mostly Americans) find it flat-out wrong, and American English is the biggest influence on most Duolingo courses (except Irish).
"From the ones that are in our reservations". I just made it up to show an extreme case.
By the way, in loan words, the original stress is usually conserved: lokánta, lámba, palyáço, dráma, sinéma, kóro, Atína, Róma etc.
Also, if an already existing Turkish word is used as a surname, location (village, city) etc, the stress is usually shifted to the previous syllable. For example, "aydın" (intellectual) is stressed on -dın: aydín. But the city of Aydın is stressed on the first syllable: Áydın. Another example is the word yıldız (star), stressed on the final syllable. But the district I'm living in, in Ankara, is pronounced YILdız.
Anyways, these are some of the peculiarities of Turkish.
Words in Turkish are stressed on the final syllable. If the word receives additional endings (except for a couple of suffixes), then the stress shifts to the final suffix, hence making the new word stressed on the final syllable again. Ex: arabá, arabalár, arabalarín, arabalarındán.
Loan words keep their original stress as the secondary stress, keeping the final ending as the main stress.