The whole point of playing a provisional ball is that you have reason to believe that the first ball may be lost or out of bounds but you're not sure. It saves you walking up to where it came down, finding it is out of bounds, or lost, then having to go back to the tee to play another one. If everyone did this rounds would take even longer than they do.
When a player sees his ball heading for trouble, he has the option of declaring it lost, in which case the second ball is now the ball in play. However, if he still goes looking for it and finds it in play, he has to revert to the first ball. In the case described, you would definitely declare the ball lost and go with the second one, as you have virtually no chance of betttering the three you now have. It can be a real oain if the lost ball is a brand new Titleist.