Remember the raghead who tried to set off a bomb in downtown Dallas (a bank was the target there, too, IIRC) a few years ago? He may have had an inclination to try that, but the FBI basically walked him through the entire process of assembling, positioning and attempting to detonate the "explosive". Sure, all the while the undercover guys who were in contact with him were suggesting other ways of making a "statement". They'd give the suspect an "out", then let him make the decisions to press on... but how much of this stuff is being handed to these unstable fools, pre-packaged?
It's anybody's guess.
It happened at least once, with the first WTC bombing, where they helped their suspects build the bomb, but failed to disable the device or arrest them before they could detonate it. They had an FBI informant in the group, but dropped the ball and effectively ended up aiding and abetting the plot instead of trapping the suspects.
Now, supposedly that hasn’t happened again since then, but who knows? If they screwed up again, they might just have been able to hide their tracks better.
The terrorist you are referring to is Hosam Smadi. He was sentenced to 24 years in prison.
There’s a lot of info on that case here:
http://www.freerepublic.com/focus/f-news/2425049/posts