Oops. We'll say it: we, like many other tech sites, may have jumped the gun on our story that the Facebook iPad app would be released on Tuesday at Apple's Let's Talk iPhone event. Unfortunately, the big day has come and gone and still the app was not to be found.

The question is, what happened? While it's no secret that Facebook and Apple have had their differences over the last few years, it did seem as though the two companies had recently reached some sort of understanding. Mashable reported last week that the Spartan Project - the fabled HTML5-based mobile app marketplace Facebook was supposedly launching in conjunction with the iPad and iPhone apps - was in fact the result of a joint project with Apple. TechCrunch subsequently published a developer image that seemed to further indicate that the Project Spartan platform was ready and positively chomping at the bit to be released.

And, of course, we know that the development of the iPad app was not what is holding up the release, thanks to developer and ex-Facebook employee Jeff Verkoeyen's blog entry that stated that the app development was basically done since May.

Many are speculating that the announcement is still forthcoming and that the delay is due to the fact that Apple and Facebook are still hammering out the conditions of their partnership. The unanswered question is why Apple would be interested in assisting Facebook with Project Spartan in the first place? All the nasty backbiting between the two companies aside, it doesn't seem to compute that Apple and Facebook would fail to partner on integration in iOS 5 only to then jointly launch an HTML5 marketplace together. The other possibility is that talks between Apple and Facebook have been put on ice. Unfortunately for iPad app well-wishers, this would mean that the app, too, would be postponed indefinitely. We'll follow the story and keep you posted.