It is a probabilistic thing. If your photon arrives at the same time as another photon, then you can have two-photon absorption (which wouldn't have occurred without your photon). Ditto if your photon arrives at the same time as a thermal vibration or any other carrier of energy. This is why semiconductors can still occasionally absorb photons with energy below their bandgap. Anything in a thermal environment has some chance of being excited, and adding extra radiation will only increase those chances.

Furthermore, if we want to get really technical and into even lower probabilities, photons don't have single well defined energies. Wavelengths are not singularly defined for waves that don't extend to infinity. Therefore, even radiation that is emitted around, say, 500 nm, still has a small of chance of being absorbed by a 499 nm transition. Obviously these probabilities get tiny as the difference gets large, but they never drop to 0, technically.

I'm not saying any of this is medically relevant, but practically everything that is quantum mechanical is probabilistic.

(I have a PhD in physics, focusing on experimental quantum mechanics)

It's exhilarating to have a long-held belief broken. Thank you!

Two-photon absorption becomes an important effect at high intensities (if I understand the wikipedia article). How do "high intensities" compare to the intensity of radiation from a phone?

See update (added footnote).