I found this sentence in a thesis that you can find here:
How do people learn abstract concepts unsupervised?
I sounds strange to me since unsupervised is an adjective (and from popular dictionaries, adjective is the only class for this word) but the noun it's modifying seem to be absent from the sentence.
My best guess here is that unsupervised may be used to modify some "hidden" noun phrase (rather than people) that I'm unaware of. Please help to point it out.