FWiW: according Jordy, Maddy was probably the most sober person that night...
So a drug overdose seems not very likely.
When Jordy and her new boyfriend Tyler left around 1:00 am there were only 5 people to continue the party while Maddy was in her tent. Also there was another tent straight from Garret who planned to camp there as well. At 2:45 am Garret and his girlfriend got an argument and called the party 'over'. They changed plan and breaked up their tent and left. Probably without informing Maddy they changed plan?
At that point (2:45am) some 'sober' truckers arrived there after their late shift and went over to Maddy's tent asking if she would like to have a ride home with them but Maddy declined because she was in bed and didn't want to leave her belongings. Not sure if Maddy fully understood she was about to camp all alone? She probably didn't and thought Garret and his girlfriend would stay to camp as well, so no 'worries'.... According Dawn Scott, Maddy's mother, she would never wanted to stay there all alone....
So Jordy said that when she left around 1 am there were still 5 people to continue the party.
But from the 48 hours info it should be 6 people: the 'Allman' brothers, the 'Black' brothers and Garret and his girlfriend. I wonder how many sober drivers arrived at around 2:45 am and who did they give a ride? Looks like we have at least 8 people (hence 'sober' truckers ) that night who could have known Maddy was about staying all alone there.....
It's almost impossible a whole group of people would stay silence for 12 years if they knew something. Someone had already talked long ago. Most likely one or two individuals saw an 'opportunity' and returned to Hogsbag after everybody was gone from the party. Maddy maybe even left with them voluntary because she had time to grab her car keys and iphone. Who knows what happened from there....