A Congressional panel suggested yesterday that the Library of Congress should look to private companies with proven cataloging systems to improve its own storage and retrieval systems. “In the past year, spot-checks have shown the library hasn’t been able to account for 10 to 17 percent of its books, monographs and bound periodicals.” But librarians say that their situation is different, and point out that the library is underfunded and doing its best with the resources available.