I agree that Joseph Park has to be a major player in the entire Aces & Eights storyline, but I wouldn't necessarily call his involvement a "plot hole" (at least not yet). As far as I understood what was happening, Joseph Park showed up on Impact a few weeks ago (whenever it was, I don't remember the exact date) telling Hogan & Sting that he was expecting a fax that would "blow this whole Aces & Eights thing wide open" (or something to that effect). I don't remember when he was supposed to receive the infamous "fax", if it was supposed to be later that night or on the next week's episode of Impact.
Either way, I think the fax Park was expecting is the reason that he was kidnapped by Aces & Eights; Park was either kidnapped by A&8s so that he couldn't reveal the information from the fax, or he was kidnapped so he wouldn't be able to accept the fax at all. Since the fax hasn't been referenced at all since Park's return, I'd have to assume that Joseph never got the information he was hoping to get. We also have to remember that Park never said he was "definitely" getting this information, just that the fax he was expecting had the potential to "blow the Aces & Eights situation wide open" (or whatever it was that he said). Another possibility is that Park did receive the fax, but it didn't have the information he thought it would...although that would be strange for a pro-wrestling plot, since why bother even mentioning it if it wasn't going to come through? ...and why would A&8s kidnap him at all, if there wasn't "incriminating" information on that fax? Either way, I'd like that question answered as well...but it obviously wasn't answered on the last episode of Impact. Maybe they'll address it later, but I think maybe we're just expected to forget about it all together.
I think it's more likely that we're meant to forget about the fax Chris Park was talking about all together, and we're now supposed to focus more on his kidnapping. When Park showed up in Hogan's office on the last episode of Impact, Hogan's first question was "what did you see?" - or whatever. The fax (and whatever info that it was supposed to contain) wasn't mentioned at all. Also, Hogan said something like "we've gotta get you in the gym" or something, which probably means that we'll see the Joseph Park character in a TNA ring - involved in a match against Aces & Eights.
Obviously Joseph's involvement in the A&8s storyline could prove to be the biggest piece of the puzzle, and that's why it seems like a "plot hole" right now (even though it's not, really - at least not yet). If Joseph's role in the A&8 storyline does turn out to be a huge part of the storyline, then that's the reason why these questions haven't been answered yet. Obviously TNA isn't going to give away a huge plot twist so soon, it's got to be stretched out so the story can progress slowly.
I'd imagine that the fax Joseph Park was expecting can still be sent to him, so now that he's "home" (no longer a kidnapped victim of Aces & Eights) he could have the fax sent again. But like I mentioned earlier, I think TNA expects us to just forget about that all together. As far as Hogan's question to Park ("what did you see?"), we didn't get any answers about that either. Park said all of that in private to Hogan (no cameras, no other wrestlers, etc), but my guess is that the A&8 members wore their masks the entire time they were around Park while he was "kidnapped" (and locked in that cage, or whatever). Honestly, I don't think that Park really "saw" anything during his time as a prisoner of the group. Then again, maybe all of that will be addressed in time. At least TNA didn't try to just breeze over Joseph's kidnapping without mentioning it at all (which they've been known to do in the past), I think that they just haven't revealed the story yet because (like I said earlier) Joseph's involvement in the A&8s storyline is such a big piece of the puzzle. There are so many possibilities of Abyss/Joseph Park's involvement in this storyline, and TNA wouldn't want to give the entire story away quite that quickly. That's my take on this whole thing, at least. I think that we'll get more answers from Joseph Park in the near-future, so it's not a case of there being "plot holes"...the "holes" are just questions that have yet to be answered (although I feel those questions will be answered over the next few weeks). We'll just have to be patient, and wait & see if those questions are answered or not. Once the whole story is revealed, there might still be plot holes - but as of now I think the story is progressing logically enough.