The first Ghost Rider race if FF Spider-Man and is on the same dock as where you get Squirrel Girl. FF Mister Fantastic is on the opposite shore and is the 2nd Ghost Rider race. I think it was somewhere near Carnage, but I'm not 100% certain. It is down a ways away from Rikers Island.
Yeah, it didn't appear for me, and I used that code as well. I actually think it won't show up because of it as well. What I think happened is, given how F.F. Spiderman is unlocked, the game removes that side quest from the map. As a result, it doesn't get counted as being completed, and the side quest that follows (the one that unlocks F.F. Mr. Fantastic) remains locked.
I am currently on my second play through, in which I'm planing on unlocking F.F. Spiderman through the side quest instead of the code. Might take me a bit to confirm the theory, but it wouldn't surprise me if it turned out to be true.
Hopefully, this can put many minds at ease. I also used the FF Spiderman code, and as such, couldn't find FF Mister Fantastic. The first Ghost Rider icon was not appearing on my map, but he was standing where someone said he would be, at the end of the dock where you get Squirrel Girl. Beat that race, and then his second race, the one for FF Mister Fantastic, did show up on the map. It took several tries, and him getting stuck behind three different cars, plus the one I put in front of him, but I won, and FF Mister Fantastic did unlock normally.
For the record, I MAY also be having the Stan Lee glitch, of that I am not sure. I knew about it beforehand, so when I rescued him, I checked my percentage before and after, and it did go up, but the icon is back on my map now. I don't know if that is going to screw up my game or not, I am finishing up the free play stuff now.