That piece of paper could have come from anywhere, and the guy might've picked it up and wrote that jr. high thing on the back, having yet to deliver it. Lou should follow Mr. Shortly and appeal to his emotions with a phrase like, "Janet payed your bounty and wants you to stop all of this, she is waiting for you right now." We have about a 25% chance that it was his, (or even if it was his dead buddy's, then his buddy might know/like her too). So he probably will ask, "where is she waiting?" or if we are lucky, "She's waiting at her house?" or something like that, giving a location. If he says the former, then Lou replies, "She says you would know." Lou tails him whatever the case, and interrogates Janet later, figuring out more about Mr. Stoutly and cohorts.