This is what happened: Two days ago, a lorry overturned two miles away spilling two tons of Miracle Gro. On that very day, a freak heatwave crossed the country, making all two tons of the plant food evaporate.
Then for a day the plant food crossed the land for two miles as a cloud. Last night, all around the campsite, there was a rainstorm of Miracle Gro, and lo and behold, today you've woken up to find the only exit of the campsite blocked by 50 foot grass. Damn. Worse still, your weirdo friend has taken it to be some sort of sign, and has decided to stand in the sacred grass until the day he dies. Damn and drat.