This scenario was discussed at our association meeting tonight, and I left thinking I was 100% right and one of our R's was 100% wrong. But after going back over the book, I think my instincts led me down the wrong path. See what you think, and if you can cite the rule that I think covers it:
3rd and 15 at K's 12. K decides to punt on third down, but the kick is blocked behind the line by R77 and never crosses the LOS. Before anyone can gain possession it rolls out of bounds at K's 4. What do you have?