State Dept. revokes 9,500+ visas over terrorist concerns--but their whereabouts are unknown. What accounts for this incompetency?

The Obama administration cannot be sure of the whereabouts of thousands of foreigners in the U.S. who had their visas revoked over terror concerns and other reasons, a State Department official acknowledged Thursday. The admission, made at a House oversight hearing examining immigrant vetting in the wake of major terror attacks, drew a sharp rebuke from the committee chairman. “You don’t have a clue do you?” Rep. Jason Chaffetz, R-Utah, told Michele Thoren Bond, assistant secretary for the Bureau of Consular Affairs. Bond initially said the U.S. has revoked more than 122,000 visas since 2001, including 9,500 because of the threat of terrorism.
http://www.foxnews.com/politics/2015/12/17/feds-cant-say-whereabouts-those-whose-visas-were-revoked-over-terror-threat.html?intcmp=hpbt1