Spider control for vehicle

Last week my daughter was bitten by a spider. she never saw it but had two distinct fang marks on her leg. I didn't know about it until she complained that her leg hurt later that evening. We had been several places that day so I assumed it had gotten her somewhere along the way. Fast forward to today. We drove into town and when she got out of her car seat she had another red mark lower down on her same leg.

I have pretty much torn the Suburban apart trying to find it. Removed and inspected her car seat, checked everywhere under the seats and floorboards. I only found one small web under the seats but it looked old and pretty ratty and no spider around or in it. I haven't found any other trace of ants or bugs, alive or dead in the Suburban. Now I'm scratching my head.

Looking for a product (other than a flamethrower) that will kill this pest. Needs to be safe enough to use in a vehicle that won't harm my 3 kids. Since I can't find the spider I need it to kill with residual residues instead of directly spraying it. Any ideas are welcome and I thank you for taking the time to help.