John Singleton Copley (1738-1815) Painting of William Ponsonby, Second Earl of Bessborough, 1790

Art detectives say long-lost works like the Copley are increasingly turning up after going missing for ­decades, thanks in large part to readily available information on the Internet or in electronic databases. The trend is feeding hopes of art fans that the prized pieces taken from the Isabella Stewart Gardner Museum 23 years ago could eventually surface as well. 

Though the vast majority of missing artwork is never recovered, stolen items are often discovered when they change hand, sometimes many years later, when brokers and buyers research the pieces online and through databases, according to brokers and others in the business.

“We’ve got recoveries happening every week,” said ­Christopher A. Marinello, an ­attorney for the Art Loss Register of London, which maintains an international database of more than 360,000 stolen, looted, disputed, or missing works around the world, including 1,000 from Massachusetts and hundreds of pieces from ­Harvard alone.

“It’s not that unusual to find artwork that has been lost for more than a quarter of a century,” Marinello said. “The valuable pieces either are recovered right away, or they go underground for a generation.”