So, Cybertrash, can you tell us what you have decided to do? I am sure we can continue to discuss this thread for quite a few more pages without your involvement but only you can tell us what you intend to do to get to a solution as it is you who has the problem.
You could of course "write off" FP4+ as not being a worthwhile film but I hope that enough of us have given you reasons why this isn't the case.
Reticulation has a very specific pattern which the photo does not show. There is an excellent example of it in Graint Haist's Minibath Manual. Sort of like a bunch of worms. Once you seen it you will never confuse it with grain.
My first reaction was maybe that this was a scan from a print on a matt or textured paper and that this was picking up a "grainy" pattern from the paper surface, which shows up more significantly when the scan is enlarged on the PC screen.
If it's not this, you really need to examine the neg with a strong magnifier or low-power microscope to exclude something in the printing. I've used FP4+ and HP4+ quite a lot recently, and 6x4 prints are substantially grainless with the standard developers I've used. Scans of the negs viewed on screen or as inkjet prints also look OK.