Lost WPA Posters?

While doing research at the University of Maryland College Park Archives, I found photographs that showed the WPA posters shown below (images are cropped from the original photographs). The Library of Congress has 900 of the "2000 WPA posters known to exist." None of the posters below appear to be included in the Library of Congress's collection. Could some of the originals still be out there somewhere?    

(All images courtesy of the University of Maryland College Park Archives.)