Give Sears a call and tell them the motor was missing. They just might
replace it free of charge. Worth a try anyway.

Absolutely do this. My nephew bought one of their upright dust collectors
this way for $50, but it was missing some components. The salesperson told
him outright to contact customer service about the parts. He did and had
the parts within a week.

BTW $59 for the motor sounds VERY OPTIMISTIC. I checked into a 1HP motor
for an older Craftsman table saw and it was in the $130 range. Or are you
looking at a rebuild?