The number of homeless military veterans across the United States — at least 50,000 in January 2014 and 48,000 in January 2015, according to the National Alliance to End Homelessness — underscores the devastating mental, emotional and physical wounds of war that afflict the nation’s heroes long after the battle ends. But there are almost certainly more homeless vets living in the shadows of the highway overpasses and Main Street missions, uncounted and disconnected from treatment and services. “It’s been here since the ’70s,” Robert, 38, a homeless Marine Corps veteran living under the Queen City Bridge in Gainesville, said of veterans slipping through the cracks and onto the streets.