It’s early season and the course has only just re-opened after a spell of prolonged wet weather. The committee has chosen to implement Model Local Rule (MLR) E-3 “Preferred Lies.”
It states that – When adverse conditions such as heavy snows, spring thaws, prolonged rains or extreme heat prevent use of heavy mowing equipment, and the conditions are widespread on the course, the Committee can choose to adopt a Local Rule for "preferred lies" to allow fair play or help protect some or all fairways. Such an MLR is supposed to be withdrawn as soon as conditions allow.
If this MLR is implemented, you will be able to take free relief on any surface cut to fairway height or lower. If you’re in a divot hole on the fairway, you will be able to get free relief. Your relief area will be defined by the committee, but it will likely be either (as recommended in The Rules) six inches, a scorecard’s length or a club length from the reference point, (the spot of the ball.)
But, The Rules recommend that Model Local Rule E-3 is not used outside the fairway in the general area as it could result in a player gaining free relief from areas where a ball might otherwise be unplayable (such as in a bush or behind a tree).
This is a recommendation, but committees should adhere to it which means you won’t be getting free relief from a divot hole in the rough when it’s preferred lies. The answer to the question of “do you get free relief from a divot hole in the rough when it’s preferred lies?” … is no, unless the committee has decided to ignore the recommendation in The Rules.
When wet conditions are throughout the course and are causing “mud balls,” there is another Model Local Rule - E-2 which allows you to lift clean and place your ball back on its original spot. This MLR can be used throughout the general area (including the rough). If that MLR is in place and your ball is in a divot hole in the rough, you could mark your ball, lift it and clean it. But you would have to replace it on its original spot, so back in the divot hole.
Basically then, if you find your ball in a divot hole in the rough, you’re going to have to play it from there, even if preferred lies are in operation, even if MLR E-2 is being used. Bad luck!