Quick Technology Question

There was something in yesterday's Times article about catching the Times Square bomber wanna-be that was very confusing to me.

The young woman in Bridgeport who last month sold Mr. Shahzad the rusting 1993 Nissan Pathfinder prosecutors say he used in the failed attack did not remember his name. But she had his telephone number.
That number was traced back to a prepaid cellular phone purchased by Mr. Shahzad, one that received four calls from Pakistan in the hours before he bought the S.U.V.

How did they know it was his phone, unless he paid by credit card (which, frankly, I wouldn't put past him).  There clearly is way to trace these, despite what I have been led to believe by Jack Bauer.  My buddy Brett offered a vague and drunken hypothesis, but if any of my legion of readers who are too shy to comment has any ideas of how this works, I would really appreciate it.   

EDIT

The Times provokes questions; the Times provides answers.  Apparently the last time Shahzad came back from Pakistan he was given extra screening and had to provide a phone number.  Same one he used to handle other transactions.   This guy really is going to go down as one of the worst terrorists ever.  I don't want to make light of things at all- clearly I am on record as saying that AQAP poses a very real threat- but I think the phrase I am looking for, regarding Shahzad, is: what a maroon.

Radical

Peter King, the Republican congressman from Iowa (not the strange man who talks about coffee when he is supposed to be talking about football) no longer even pretends to believe in the Constitution.  In talking about the arrest of the man suspected of the attempted Times Square bombing- who, despite having a funny name, is an American citizen- King said,

“I hope that [Attorney General Eric] Holder did discuss this with the intelligence community. If they believe they got enough from him, how much more should they get? Did they Mirandize him? I know he’s an American citizen but still,” King told POLITICO.

Really?  "But still"?   Is King really that afraid of these guys?   And, honestly, if eagerly wanting to destroy Constitutional rights doesn't make you an enemy combatant, I don't know what will.

Look, if this guy is guilty, I hope he is prosecuted under the full extent of the law.  We are in bizarre times when the phrase "of the law" is somehow weak and squishy and possibly even traitorous.  Foreign terrorist suspects are a gray area, in which I am on the side of civil courts, for a number of reasons, but I admit there is an argument.   I think what it comes down to is that if the bomber was a Tea Partier, an anarchist, an anti-abortion loon or any kind of traditional American terrorist, we wouldn't be having this debate.  His crime is compounded by the belief behind it, which, while surely not better, is hardly worse than anyone else willing to slaughter for an imagined Kingdom of Heaven.  

Also, Glenn Beck is in favor of Miranda rights for this guy based on his citizenship.  When Beck is more sane than top Republicans (and Joe Lieberman), the swing has officially gone around the bar.

(link thread via Sullivan)