I might add, that if you call a bobcat in and the cover is really thick, the chances of seeing it are slim. They are just so sneaky and they blend in so well that seeing them will be tough at best.
One thing is for sure, keep trying. No matter how good of a caller you are, you will go through periods where it seems that the coyotes are all gone because you can't buy one so to speak. This time of year is tough. Don't give up, you'll get one sooner than later.