Sorry to hear it, people should at least have the decency to text if they can't make it - it would cost them all of 10 seconds. I'm sure a lot of those same guys would cry foul if and leave a shitty review if you happened to cancel without letting them know, courtesy should work both ways.
I don't suppose there's anything ye can really do though.. maybe try encourage guys to make bookings through PM? I dunno.