If you ever make a paper negative with MGIV and then develop in Dektol you will note this combination has no visible grain.
Ya, i've done this before, too. I've never been able to find grain in paper negatives; on a light box, the texture from the paper is even more visible than the grain, in a host of different developers.

As to the suggestion of the neg. being too grainy, that's probably the case. Unless the grain is fairly large (like Delta 3200 large), it may not be immediately apparent upon visible inspection of the neg. Have u looked at the neg. under a loupe to see?