Did the us government leave pows in vietnam

As for the official statement by the United States Government it denied the leaving behind of any prisoners of wars (POW’s) in Vietnam. According to a report when the war ended in 1973, five hundred and ninny-one prisoners were returned to the US Government and it was declared that that is all the prisoners they had but more than 2500 Americans who fought in the army were still missing. The issue has been a troubling one since then, many evidences were found about the prisoners kept alive but a few recovered. 

excuse me, so what the hell is the