Megan Bell, from Seaham, County Durham, died at T in the Park in 2016 and had "extremely high levels of ecstasy" in her bloodstream, the inquest heard.
A "gap" in evidence meant it was not possible to tell whether the 17-year-old had voluntarily taken the drugs.
She died "very quickly and tragically", Crook Coroner's Court heard.
Miss Bell collapsed on the first night of the festival after visiting a dance party tent and could not be revived by paramedics.
Northumbria Police is continuing to investigate whether the drugs were purchased before going to the festival in Strathallan Castle in Perthshire.
Her parents are campaigning for better safety for young people at festivals.
Chris Bell, Megan's father, said: "She loved music, singing, dancing and went to drama school when she was younger.
"We knew she wasn't a regular drug user... and somebody has given her something that's killed her.
"In her words she said 'I'm not daft dad, I know what I'm doing' and unfortunately she never came back."
A teenager who died after taking drugs at a music festival in Scotland might have had her drink spiked, an inquest has found.