Scientific Research Corporation Senior Software Engineer interview questions

I went through several phone interviews before driving down several hours to an interview in person. The company paid for me to stay at a nice hotel for the duration of the interview. The interview lasted more than four hours. I thought everything went pretty well. (Someone working there got chastised for taking me to a bathroom in a "secure area," but that wasn't my fault.) The manager promised to let me know whether I got the job in a day or two. A couple of days went by after I got back, but I didn't hear from anyone. I e-mailed the HR contact I had, and no reply. I called the HR contact several times over the next few days, just trying to get some kind of response. I never heard back from anyone. After all the trouble they went to, someone at least could've said "Sorry, you're not what we are looking for." That was so unprofessional. I have no idea what I did wrong; I showed up in my best suit and I can't remember any faux pauxs or poor answers. I have successfully interviewed many times at other firms. In any case, the least these people could've done was give me an answer. What a giant waste of time...