But before they could even think about the script, which this year won them the screenwriting award at the Sundance Film Festival, they needed to find the advertisement's author.
"We really bought the rights to those six sentences as if they were a novel," Trevorrow says.
"I had to track this guy down at the magazine he writes for, which is called Backwoods Home. It's out at northern Oregon."
He called the author, John Silveira, and they met. Silveira had placed the faux ad in his magazine as a joke to fill space. Still, he was suspicious when Trevorrow came calling.
"He actually brought a gun with him to the lunch, cause he carries his own weapons wherever he goes.
"We really had to form a friendship in a lot of ways," Trevorrow says of Silveira and in the months that passed from their first chat to him finally signing over the rights, that was what happened.
"The [time] was spent very slowly getting him to trust me and to have confidence and faith that I wasn't going to ruin this thing."
"It really is an important little piece of writing and especially in his life, in that ... it's going to outlive him, it's going to outlive me. I mean, it's a movie now."
Safety Not Guaranteed stars the deadpan Aubrey Plaza, who had the role of disillusioned college grad Darius written for her after Connolly saw her in the Judd Apatow/Adam Sandler movie, Funny People.
While interning at a magazine, Darius finds herself covering a story with fellow intern Arnau (Karan Soni) and their party-hard boss Jeff (New Girl's Jake Johnson).
Their job is to track down and do a tongue-in-cheek investigation of the owner of the ad (played by Mark Duplass who is currently to be seen in Your Sister's Sister) and see if it's real or a prank.
Trevorrow says he personally isn't sure whether time travel is possible, but has found things like Facebook have certainly affected those memories people might want to revisit.
He says in any other time, you would never be able to find that person you loved when you were 12.
"Now you can find him and you'll see that he's 50 pounds overweight and it might ruin that special memory that you have," he says.
"I think Facebook broke the rose-coloured glasses to a big extent and I don't know if that's a good thing or a bad thing.
"It's almost made me want to not find certain people, because I want to keep those memories where they are."
In Safety Not Guaranteed, one character finds someone special from his youth and describes that feeling.
"Jake says it in the movie, like, 'you're like a fantasy in my head. You're like a unicorn essentially'," Trevorrow recalls.
"There's some people ... I want them to stay unicorns."
What: Safety Not Guaranteed, directed by Colin Trevorrow, starring Aubrey Plaza, Mark Duplass
When: Sneak previews this weekend, opens at cinemas on Thursday
- TimeOut / AAP
