Missing teenager Jay Slater could be alive and surviving on just “rainwater and plants”, a private investigator has claimed. The 19-year-old flew from Lancashire to the Canary Islands for a music festival but disappeared after he went to stay with people he met during a night out on June 16. During his final call to his friend Lucy Law at 8am local time on June 17, the 19-year-old said his phone had only one per cent battery, he was thirsty, and he did not know where he was. His last location showed he was in the Rural de Teno Park – an area popular among hikers. He has not been seen since. Th…