There are few rules. Masculine mostly end with russian consonants. Feminine words mostly with russian vowels and neutral gender words with either o or e. As usual, there will be some exceptions for some words. Ex: папа(father) ends with 'a' which is a russian vowel but is a masculine word.
Perhaps it's time to change the device's language instead. And if that's the technique you currently use, it should be on the top letter line, the fifth from tab.
I suspect you might be overlooking it, though. I think it'd be in the same place in that instance. But really, I can't see why one of the letters wouldn't be included.
It will be accepted on this course - personal experience - if that's the answer, but it's better to stick with translating /all/ the words provided in the sentence for sake of practice and memory. It's not a pleasant thing to realize you've omitted something so much that you forget the meaning, even more when it's so basic.