Not the reply you probably want, but I'd be looking at the problem rather than the cure.
For starters, I'd try and find out where they got out, then secure the yard.
As others have said, tracking dogs with a drone is difficult (tried it recently on holiday to try get some pics). First you would have to find which direction they went, then scan around for what would be minute images of them from above.
Chances are, you or someone would have already found them on foot by the time you would by drone.
Or, they'll come wandering back on their own as if nothing has happened when it's dinner time
