actually no, some of it gets absorbed. that’s why there are SAR values available for all cellphones. it measures how many watts of heat get absorbed per kilogram of brain.
since it’s non-ionizing though, the only effect is a slight heating. like microwatts of heating. 15 minutes in direct sunlight is equal to millions of phone calls. but we do measure it!
No question it causes a little heat when it bounces off and the heat is absorbed, but if that heat gets to the point where you’re causing damage cooking yourself with a phone the phone is seriously malfunctioning and broken.