"¿Qué bebiste en el restaurante ayer?"
Translation:What did you drink in the restaurant yesterday?
There is an algorithm that is used to check our answers. You have to realize it despite the apparent notion that a green anthropomorphic owl hears you and reads your writings, it is not so. This algorithm should not be too strict in order not to discourage some people, not too lenient in order not discourage some other people (and achieve some educational outcome) and not too random in order not discourage some other people (like you). See how the task is not easy?
Once the algorithm is set up (and then constantly tweaked), the computer executes it. It has no pity or mercy, no understanding of severity or insignificance of an error, so your assertion that that is 'petty' is not applicable here.
As for advice: either ignore the sting of Duolingo's algorithm-driven corrections or learn to spell words correctly.
"Learn to spell" was a tongue-in-cheek part of advice. You yourself stated that you do know how to spell 'restaurante', it was a simple case of missed letter. I think I did a pretty good job describing the workings of an algorithm and suggested not paying attention (or feeling a personal affront) toward a mindless and heartless machine (technically, software). But you see what you see.
You are not paying me or anyone here. We are your fellow learners. You do not even have to pay 'fir' this service at all, although I am glad you do: you are supporting a worthy endeavor. Thanks.