Did you find other signs such as fresh scat or tracks? There are a lot of reasons they will stay quite. When I run into no sounds, I pay more attention for other signs. Where I hunted last week we ran across a few elk that were making noises but kept very low key I assume due to hunting pressure. The bulls seemed to be rounding up cows even as warm and dry as it was. Everyone we located had 2 or 3 cows with them. Even if you don't hear all the sounds that go with the rut, the rut still happens regardless of weather or other conditions. Since I hunt a heavily pressured area, I rely on other signs more.