Without context, that has to be accepted - it could have been a toy bus (or someone who actually owns a bus company). As long as you knos when to use it, Duo has to accept it as a correct answer.
I don't think Duolingo should take into account EVERY possible context. Firstly, because it would be impossible. Secondly, because it messes with our perception of what is the most common usage. And third, language is not about finding a context to fit what you say - it's exactly the other way around.
It is very difficult when English is not our mother language :)
Thanks again Rafael
You're welcome Milelama! Sorry if I sounded too direct or dry in my answers. :)
I understand your point of view, but I don't think the option of accepting legitimate translations suggested by users is so terrible and certainly not impossible. This discussion area is where the wheat (the most common usages) can be separated from the chaff (the more left-field uses). The course contributors usually do a good job of making sure that only the best translation pairs are used in the exercises.
About your last point, I would agree entirely if I were the one speaking or writing, but I'm not, I have to interpret Duolingo's sometimes odd sentences and then it is often all about finding an appropriate context.
I have to agree with Luis here. Perder - to miss, to lose. A native speaker would immediately think 'I missed my bus', yet 'I lost my bus' is a perfectly acceptable alternative from a grammatical viewpoint.
It is perhaps not too bad an idea to explore other options besides the generally accepted answer. It leads to lively debate, as above, and we all learn more about the subtle differences a word can have.
Unfortunately, it isn't. When you say that it sounds like the bus was actually yours, like you really bought it and then lost it, as if they were keys.
Aqui em Portugal ha uma outra palavra por "bus": "autocarro", e se usa mais frequente.