Pazo de Fonseca Exhitbit Center website

Well, Anemone, another way to try to find him is to search more generally for Spanish painters who painted about the Civil War, since there probably aren't that many, at least not who lived in Spain and painted in the aftermath of the war. I'm guessing it's not Picasso, Dali or Miro. Do you know where and when he painted? Can you describe the type of painting a bit? I love these little treasure hunts.

http://pinturasguerra.blogspot.com/2014/11/pinturas-sobre-la-guerra-civil-espanola.html

https://prezi.com/m/va92kvgbrf6l/arte-durante-la-guerra-civil-espanola-1936-1939/

There's someone named Horacio Ferrer: http://www.museoreinasofia.es/coleccion/obra/madrid-1937-aviones-negros

There are also painters from other countries -- was this guy a Spaniard? If not, the plot thickens: http://impactoguerracivil.blogspot.com/2011/05/artistas-en-la-guerra-civil-espanola.html

But maybe, just maybe, it's this exhibit: http://xornal.usc.es/xornal/acontece/2015_05/noticia_0050.html

Hope this gives you something of a lead, and if you give me more details, I would be happy to keep searching a bit!