TV episode, detective given phone number on dollar bill and spends it.

Can anybody remind me from which show this episode was: A male detective, (I'll call him Joe but that's not his name) (Not one of the main characters but a regular character, not usually this incompetent), gets given a phone number by a mob informant and is asked to give it to the main male character, (I'll call him Peter, again not real name). Trouble is, Joe is getting his drink on in a bar and barely comprehends what the informant is saying. Informant eventually writes the number on one of Joe's $1 bills in red pen.

The next day Joe finally remembers the informant at the bar, and that he had time sensitive information that he needed to tell Peter. He then remembers that he spent the last of the money at the bar. Peter and the female main character, (call her Karen, not real name) then have to track down the dollar bill. This leads them to the bar, to the customer who changed a large bill, to the stripper he gave the $1 to, and the shop the stripper shopped at, all the while the deadline is ticking away. When they finally get the number it's too late and the informant is shot when the phone call comes through. All the while Peter and Karen are covering for Joe.

Although they catch the bad guy, Joe's incompetence caused the death on an informant and made the case a lot harder than it should have been. This is basically laughed off though, and Joe is still there in the next episode, apparently no consequences.