Okay, I suppose I'll give it another shot. I honestly don't remember skipping a gym - I just know that I've beaten the Millenium City gym, and all the events in that area, and I still cannot use Fly (or Strength, but I figured the 8th gym would get me that one).
For trying to return, I know that DRG had said that if I was at DR:HQ, I should take the Huntik route cave entrance to get back to Millenium City, so that I am in the main world area. But that does not help, as to the north from Millenium city is the wavepool area that leads to the den that Kyurem is in. I cannot go further north than that, but it appears that if I could, it would take me back to the starting city. Travelling the other way, I head into the Twilight Zone area, then back to Montage Port, then through all the desert areas (Forbidden Sands, Inferno Mountain, No Man's Land, Desert Point), arrive in Novella Town, then take the Straight Path to Numassity City, where I cannot go any further, as Kai's Dad is blocking my route south of there.
Sorry for the lengthy description of my route, but I wanted to show that nowhere in that route is there a branch or a different path I can take. I am stuck between these two points, and have no way to get to any of the following: Iceland City, Salem, Mystic Falls, Atlantic City, Waters Cavern, Flamen City, Lavaburn Forest, Tiki Village, and Fells Town.
I did not mean to be careless by skipping the Iceland City gym - I believed I was following the intended storyline and route. I am now just looking for a way to get back and finish up the game.