"I'm in trouble. My wallet is missing."
Yes, こまりました is the polite past form of こまる.
困る 【こまる】 to be troubled; to be worried; to be bothered; to be embarrassed; to be stumped
So if in the sentence the person is presently in trouble should it not be こまります？
If it helps, in English you also usually say "I'm troubled" for the present tense.
こまります means “I will have trouble”. こまりました means “I have had trouble”, i.e. “I am in trouble”. They are conjugations of the verb こまる (“to have trouble/problem”). More: https://www.duolingo.com/comment/23184916$comment_id=25386021
While こまります does indeed mean “I will have trouble”, it also means "I have trouble". There is no difference in Japanese between the present tense and the simple future tense.
Interestingly, Duo accepted 困っています for me. Wouldn't the ている form be more appropriate for describing a troubled state?
I used the て form and put わたしは in front of こまっています, but was marked wrong. I'm assuming it's just one of Duolingo's quirks in this case.