Even though AT&T's $30 unlimited data plan technically went the way of the dodo back on June 7, the company had assured 3G iPad owners that they'd be entitled to one last hurrah -- buy an iPad prior to the 7th and you'd be allowed to grandfather into the old plan, even if you didn't receive your purchase by the deadline. Problem is, the unlimited plan option finally disappeared off AT&T-connected iPads for the first time today, leaving some of these eligible folks who haven't yet signed up for 3G data in the lurch. Not to worry, though: AT&T says that everyone who's eligible "will be able to select the unlimited plan" and that "details will follow." In other words, we don't know how this is going to work yet, but at least the carrier's aware of the issue. Stay tuned.