"I have been mugged!"
Translation:Jag har blivit rånad!
Even if you could have said that, that would not translate this sentence, but rather I was being mugged (where I still think that is a much better sentence in English than Jag rånades is in Swedish). We do accept Jag har rånats! here, but I would not recommend it for the reasons Anders91 mentions, also there is this thing that the -s passive typically focuses process rather than result, which means it gets extra strange without an agent or some kind of adverbial describing the process.
That's because Jag blev rånad has a perfect counterpart in I was mugged — those two have the same time. I wish it would always show Jag har blivit rånad since that's the recommended answer, but we can't control which accepted answers Duo shows – the machine tries to match what you input, and sometimes the result isn't optimal.