You might be able to tell by looking through the front of the light to see if it's blown. Sometimes it's obvious, sometimes you can just see one of the filaments (fine little wires) is not contacting both ends where it should be to create the circuit. Sometimes with the lights on you can give them a hit and the filament will recontact and start working all of a sudden.
I've presumed bigger problems before due to two lights being out only to find out after wasting time it was just two globes gone!
It seems unusual that everything else works, just not two (of 4)headlights.
Start with the basics first- globes, power then earth.