Yes, you're in this for tiny survival, but you're still a human being, and you're not going to spend any more time than you have to hanging around some ignorant girl's feet. Rachel only felt you because you made your attempt to climb on her bare skin; to remain undetected, you'll scuttle up the thick denim jeans that Taylor is wearing. You'll get up from the dank footwell and have this trip in something approaching comfort.
It's much easier, threads having greater gaps to grip than the warm, living skin of a god-woman. While you do so, over the chattering of the radio you can hear the conversation of the Andersons.
"Look," Ethan snorts, "it's just a prank, right? Guy left a note, scared us a bit, no harm."
"Her was in our house, Eeth," Taylor emphasises, turning slightly in her seat to look her brother in the eye. Her leg moves a little, but not enough to throw you off. "He could have done anything while he was in there. This 'shrunken' thing he's on about? That's some Saw-level mind game shit, bro."
"Language," Rachel asserts with a firm tone, and besides a brief giggle from Abby that puts a stop to the talking.
You throw yourself up over the teen's knee, and stop to draw a few shuddering breaths before looking around. At 1/8" tall, you're not going to be noticed unless someone looks directly at you, and with Rachel over there keeping her eyes on the road, Taylor is the only one who might spot you. Looking up, you see her gigantic fingers holding your note before her face, the girl reading and re-reading your statement as if she thinks she could find a revelation at any moment. You hope you haven't spooked the poor lass too much.
So, she's distracted, and you could happily sit out the rest of the ride to Lisa's house right here. But there are other places you could go, from Taylor's pocket to that comfortable and secure cup holder over there. You could even try to get back to Rachel herself, using your newfound vantage point to avoid that embarrassing itch you caused earlier.