We all know that the rules say, that if there is suffiecient evidence (such as witnesses or the like) that point to the ball being lost in a water hazard, the player are allowed to get relief according to normal rules for taking relief from a hazard.

The same goes for "abnormal ground conditions".

But what about "Ground under repair"?

I can find no reference to that in the rules, and while the idea about sufficient evidence seems somewhat reasonable, there is ONE huge difference between "Ground under repair" and hazards, namely the loss of stroke.

Taking relief from a hazard costs you stroke and distance. Taking relief from Ground under repair costs you only distance.

Also - Ground under repair is not necessarily a place where you can't play your ball, you can CHOOSE to take relief, but don't have too.

Because of this, my assumption is that you MUST FIND THE BALL in Ground under repair in order to take relief from that. If you don't, I would consider the ball LOST, forcing you to replay your last shot and card a 1 shot penalty!

But what do YOU think? Would YOU accept a call of "can we agree that the ball is in the Ground under repair" and allow a player the "free" drop and possible improvement of lie? Or would you insist on the ball being LOST and the player having to go back and replay his shot under loss of stroke and distance?

I can't find anything clear in the rules or decisions.