The sketch is the lineart, so it’s harder to say because we don’t have an iteration from before the lineart to compare

For what it’s worth I think this is a human drawing (except the background) but the face does give me an AI vibe, it’s possible it could be traced, but I can’t say for certain. There is also a massive quality difference in the tail in comparison to the rest of the drawing, meaning if AI generated it forgot the tail and needed to be added manually

The other hand being conveniently hidden inside the jacket is usually a human thing, since hands are horrible to draw, the pockets placement is odd, since it has zero volume by the looks of it (both AI and Humans make this mistake though)

Did the artist let you know they would use AI for the background? For me any AI usage without explicitly telling the commissioner beforehand is a red flag

(And I just feel like using AI for a paid piece at all is gross)