The issue with this is that, sure, you can see things with your sensors if you are looking at them. But the ability to see a single face doesn't mean squat in terms of finding that face from the surface of the planet. Might be a search for the face would take fifteen thousand years on the average.
Using phaser beams as emergency flares is attractive because they are very visible and visual things. They glow to the sides a lot, and immediately indicate the point of origin as well. You don't need fancy sensors for that: plain or moderately augmented eyes will suffice.
We have little idea what a hand phaser beam would look like at the apparent orbital height of a thousand kilometers or so (ships seldom are seen higher up, because it's important to have a good look at the cool planetary VFX, too). We know that beams from starships suffer no visible spreading out or degradation across such distances, though. Except when they are weak beams, as in "Return to Grace"... So perhaps a weak hand phaser would be prone to dispersing where a starship phaser bank is not.
Timo Saloniemi