Geometric interview questions

I was interviewed at bangalore. The interview consists of three rounds aptitude test, group discussion and technical and hr. Aptitude was of moderate level I cleared it, and in gd out of 11 students I was among the 3 students to be selected. Next day technical and hr round. In technical round I was asked basics of som, gd & t, and orthographic and isometric projections. I did well. But till today I cannot understand why I wasn't selected even after going to technical and hr rounds because its considered that the selection is 99% guaranteed when you reach technical & hr round. If anyone could tell reply me...

the interview process was very brief and was a phone interview. there was one round of interview and the follow up process took around 8 - 10 days or 2 weeks if i remember correctly