There is a glitch in the US app that checks you in but won't email you a BP. Its happened to me frequently. I always make sure that I get to the airport in time to check in with an agent (for work I must always check a bag). Its frustrating but sadly cut off times are tight because that agent then must get to the gate. Likely it was a contract worker. Still, some consideration should have been made. Good thing is that of 10/17 it all goes to aa.com.