I asked a question on Stack Overflow and it never showed up and my profile page never indicated that it was asked. What gives?
Assuming that you asked the question as the same account... there are no deleted questions against your account; therefore, the most logical explanation is that your question was merged with another (very similar) question. Currently, merged questions leave no traces... which is unfortunate.
@Jeff: this raises the point; should a merge perhaps leave a place-holder, like migrate does?
The only other option I can think is that the submit button failed...
So that we can investigate properly... a "roughly when" and a "roughly what" would be hugely useful.
It may have been deleted by moderators. That would be the most logical one.
It may have also been migrated (but I believe that these remain on your profile) to one of the other sites.