Sneak away to meet your mistress. ("Hiking the Appalachian Trail" is the first explanation of where South Carolina Gov. Mark Sanford was when he disappeared.)
"Has anyone seen Jawann? I've been calling and texting him for three days and he's not answering."
To be so heavily under the influence of a psychedelic or dissociative substance that you are unable to distinguish normal reality from the magical reality that has taken hold of your mind. Seeing pixelated kaleidoscopic patterns in the carpet, being afraid to open the freezer because you're afraid that the fishsticks will attack you, and the ability to talk to squirrels are some sure signs that you're hopping down the bunny trail.
To be unfaithful to one's partner e.g. in an extramarital affair. Named after South Carolina Governor Mark Sanford, who was said to be hiking the Appalachian Trail, when actually he was visiting his mistress in Argentina.
"My husband has a lot of "meetings" and "conferences" to attend to lately. I think he might be hiking the Appalachian trail."
To have a sexual encounter or affair, named after the infamous disappearance of South Carolina Governor Sanford, originally thought to be hiking the Appalachian Trail, but was having an extra marital affair in Argentina.
I wanted to Hike the Appalachian Trail in the back seat of my dad's Lincon after prom, but my date wasn't drunk enough.