Few things to hopefully help you all out.
1) If you bag somehow ends up inside a tree (this should be extremely rare) you can reach into the tree and pick it up by the handle of the bag and move it. Alternatively you could also just select a club from within the tree.
2) If the ball is not hit-able for whatever reason, be it right next to a tree, in the water, out of bounds, lost in a bush, etc. you can declare the ball unplayable by taking a new ball out of the golf bag pocket. This will cost you a stroke, just like it would IRL.
3) There is an option to turn on mulligans in the gameplay settings menu. Using a mulligan will strike your score cards from the leaderboards, but it is an option if you don't want to take a stroke penalty.