Totally. They did not simply leave her somewhere thinking she was "bad off" and would "sober up and make her way home."
They left her because they played a role in her condition and were unwilling to take responsibility for it by doing the right thing: calling 911.
There are several reasons why this would not make sense.
1) It would obviously trace back to them anyway!
2) They could have still called 911 and left her outside.
If you wanted her to be found why put her in an alley?
3) Such an irresponsible act could result in her rape, death, etc...
Where they would be linked anyway! Remember JR and LS go way back with family ties and being at the same summer camp. Is it more reasonable think that JR was that much of a sociopath that he would abandon her and then make up a story that she was at his place and walked out?
However, there is a way I could see this happening temporarily and it fits with the way I see it going down.
CR carries LS over to the place where her wallet/purse and keys are found. Something happened there. Maybe he was exhausted, maybe he tried to get her on her feet, but they paused there for some reason. Then he makes it over to the dumpster area behind 5N. Here he leaves LS, maybe still alive, maybe dying, maybe dead. The timeline is really important. This is happening right around 3:00am. But MB's call to JR is not for another 30 minutes. It is this time gap that for a long time gave some credibility to the idea that LS actually had made it to CR/MB's. But that's the only thing that does! In this 1/2 hr, CR makes it back to his apt. And by 3:30 MB is calling JR. It seems doubtful that MB saw LS because he did not describe her accurately in any way. There are no doors out the back of 5N, so not easy for MB to run out and check. Perhaps there is a window he could see her from, laying by the dumpster? Alive or dead there was some drama at CR/MB's until MB finally called JR. When I play out the scenarios of CR either trying to revive LS, or realizing that she is dead, it takes time either way.
I come to think that he would be down in that gravel lot with her for at least 10 to 15 minutes. So that gives him roughly another 15 to 20 minutes in his apt. Now by the time JR is called CR and MB have to be considering the possibilities (call 911? Call JR? etc...) After JR is called there may have been a face to face discussion lasting another few minutes. So by this time if JR goes down to check on LS (alone or with a house guest) there are 3 possibilities: 1) she is gone... so then why implicate yourself in an elaborate story saying you saw things like keycard / fake id and black eyes? So that doesn't wash with me. 2) She is still there alive... so at this point wouldn't it be risky to just go back home and leave her there? So back to the other decisions... take her to the hospital, call 911 or take her to your apt? 3) She is there and is stone cold dead... now for the same reasons leaving her there alive are risky, obviously leaving her there dead is just as bad if not worse. What is most likely? Consider then 3:30 MB calls JR and takes a few minutes filling him in a bit... then they meet in person for a few minutes... then JR goes down to check on her, that takes a few minutes. We are approaching 4:00 here... but by 4:15 calls are being made to DR and ?? by JR(was that landline or cell?, because if mobile phone then he may have been down there in the lot, even a wireless landline might reach there)
So my point is that if she were left there it would have most likely been by CR and then later when JR became involved she was taken away.