[thejeff]

As far as I know, no.
But Dryads are Stealth 25 and thus hard to find to start with.
Normally, leading stealth units subtracts from the commander's stealth, but Satyr Sneaks are Stealth 20(?) and thus don't.
Unrest also drops the chance of stealth units being found. If they were able to keep the unrest up high enough, your chances of finding them could be low, even with hundreds of patrollers.

Or, they could have not been there.