omg I signed up just to comment on this because this exact thing happened to me. My professor lagged so hard that he sent it in late for at least 2 weeks. I asked him in September of 2015 and he didn't sent in until late January. Not only that, he did not send it to all the schools I asked him to send. I was rejected from three schools with an early Dec deadline (UCSD, University of Washington, and Riverside). During that month I was stressed as balls as I was out of the country and could not find him in person. I finally made him respond by emailing my undergraduate adviser to put pressure on him. With that, I was able to make him write my letters. Thankfully all turned out well and I was accepted to USC and UC Irvine, both are decent schools. Still waiting on UCLA, Rice, and Boston University. I cannot force him to write it but I was legitimately pissed off at him. He destroyed my chances for three schools.