By MELISSA GOLDIN Republicans, including former President Donald Trump, have recently claimed that hundreds of thousands of migrant children who crossed the U.S.-Mexico border unaccompanied are missing, then criticized the border policies of the Biden administration and Democratic presidential nominee Vice President Kamala Harris. Ohio Sen. JD Vance, the Republican vice presidential nominee, repeated the claim during Tuesday night’s debate. “We have 320,000 children that the Department of Homeland Security has effectively lost,” he said as he met Minnesota Gov.