I thought the same thing about the tuning fork bit- turns out there is absolutely no reliable evidence that this works. Back when I had a stress fracture later supported by a positive bone scan, the tuning fork was uncomfortable, but it was uncomfortable on my other shin as well.
Bone scans measure uptake of divalent cations to the area, so intense uptake supports a fracture, also supports a deep bruise, infection (usually why we get them in the hospital), tumor, basically any bone more active than the surrounding bone.
MRI can detect inflammation, tissue swelling in the bone, and various other more technical things that radiologists can use to help support a stress fracture.
Ditto with CT scans
Plain x-rays are useless early, may show a LARGE stress fracture, or healing bone later.
Basically, there is no way to tell with any certainty by examining the foot/leg, imaging modalities can make it a more cetain diagnosis, but the end result is the same as for a deep bone bruise: rest, eat well, and build up slowly when you return. Take the downtime to strengthen the muscles/tendons around the area.