Yes, Jupiter, that is how the theory would follow through with one addition: before she went looking for the guy with the coke, she went looking for money since her plan to get cash from her apartment was thwarted by "the altercation". To repeat what Imkeylime has already stated. LS goes to JR's apartment, tells him she can get some coke but needs money, which he gives to her. Now we have an explanation for his caginess. He doesn't want to admit that he supplied LS with money and let her go off alone to purchase drugs from a stranger in the middle of the night. Whether or not he was going to partake of the drugs himself, the moral and legal implications give him reason to lie. I hadn't thought that the call to DR was to find out if he'd seen or heard from Lauren, but it seems possible.
Disclaimer: The above is a theory based on the growing collection of hearsay and rumors that share a common theme.