A teenager was found hanging after her desperate plea for help went unanswered because her father's mobile phone was on silent.
Alissia McCoid, 18, texted him saying "Ring me now ASAP, I need you now" – but he did not receive the message until the morning after her death.
An inquest heard that the teenager could have been depressed after taking mephedrone, a formerly legal drug, also known as MCAT and Meow Meow, which was banned by the Government in April.
The court was told the teenager had taken a cocktail of mephedrone, Diazepam, vodka and wine on a night out and returned to her home in the early hours.
She was found hanging at her home at about 11.30am on February 7, by her stepfather Andrew Hunt.
Six hours earlier, at 5.35am, she had texted her biological father, Simon Deyes but his phone was on silent and he did not notice the message until the next morning – after he had been told Alissia was dead.
The court heard she had taken mephedrone for the first time on New Year's Eve and continued to use it regularly with friends over the next five weeks.
Her mother Denise McCoid said she had noticed a change in Alissia's mood and that she had "rings around her eyes".
Speaking at the inquest, she said: "She had more nights partying and was looking run down. I noticed she looked withdrawn.
"She was snappy and she started getting spots all over her face and had dry lips."
Only days before her death, her mother overheard Alissia whispering to her sister Carmen and confronted them. She said: "They said they had been taking MCat, but I didn't know what that meant.
"They explained it was only plant food and they said it was legal – as if it was normal."
Mrs McCoid broke down in tears as she said: "But teenagers, you can't say anything to them, you can't advise them, they always know better."
Dr Anne Campbell, who performed the post-mortem examination, said the mephedrone would have had an effect on Alissia's mental state.
She said: "Mephedrone is a stimulant rather like an amphetamine. When you first take it, it would make you feel elated but, as is common with other drugs, when the effects wear off you can feel low."
Alissia, who lived off Beverley Road, in Hull, had been to the Welly Club in Hull, with her sister, on the Saturday night.
There, she met her ex-boyfriend Daniel Senft, who told her he could not see her as he had reunited with his former girlfriend.
She apparently took the news well and they went on to the same house party together. Later that night she was seen crying by friends and, at some point, made the five-minute walk home alone.
In a letter read out to the court, her heartbroken mother described her as "a lovely, vivacious girl at the threshold of life".
Coroner David Rosenberg concluded the mephedrone would have affected her judgment. He said: "We have heard the evidence that it was a powerful stimulant which made you feel very happy, but when the effect wore off, made you feel very low."
Mr Rosenberg recorded an open verdict, because he said Alissia may not have intended to kill herself.
He said: "It was clear her mental state had been impacted upon by her use of mephedrone and drink.
"No one knows exactly what state she was in that morning."
Dave Mays, owner of the Welly Club, said: "Our sympathies go to the family. It is a tragedy someone so young has lost their life.
"We operate a zero-tolerance policy on all drugs."
Mephedrone became a Class B drug, after it was linked with the death of up to 25 people.