Maria Rivera stumbled upon an original Giovanni Batista Torriglia painting and instantly knew it was something special.
Rivera said the work of art looked exactly like another one she had seen in a museum.
The store had it appraised and discovered the authentic painting was worth between $12,000 and $18,000.
Goodwill has since put the painting online and drawn in thousands of dollars in bids. The auction ends Jan. 16.
For more information, visit www.shopgoodwill.com.