I am thinking the child's drawing is of a van in the Chevrolet P30 series or "step-van" series. Notice the long door on the side. These vans seemed to have annual models for decades prior to 1991. My guess would be 1981 Chevrolet Grumman Step Van.
With the white van below, note how the windows match in the sense that there is both a window on the side door and the general shape of the passenger side windows can be seen side-longed -- just like in the drawing.
These kinds of vans look like modern UPS vans. They also seem to be food-truck vans or ice-cream vans. I wonder if someone would also like to camperize a van like this, suggesting to me that Michael might have been abducted by the lodger of a campground or RV park. Picture the white van below as brown and it resembles the child's drawing.
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