Minor further comment on your post, that has much to commend it. The words above could be misunderstood that you do not need to take account of input/information from others. I do not believe that is what you are suggesting, but think it worth affirming that while each of us need to decide on all the facts, the information/facts that others bring could be a critical part of the decision making.
I also suggest a player can certainly be "proved" wrong even without finding the ball if the player claims KVC is met when there is significant foot high rough bordering a penalty area and the ball was not seen to enter the penalty area. That doesn't prevent a player playing from a wrong place, but it does enable others to protect the field appropriately.
Yes, he can be proved wrong, but he could still have a case that he listened to all info, took due diligence and believed he made the correct decision and should suffer no reprimand or penalty.
The committee would have to adjudicate accordingly if the player, or anyone else, makes an appropriate submission. The 5% doubt versus 95% certainty is what is in question. It can not be proved that the player did not have more than 95% certainty, if he said he did have more than 95% certainty and acted accordingly. The committee ruling against him has to have grounds to state that his
judgement of more than 95% certainty was in serious error and give reasons for their judgement.
This 95% business is never going to be a clearly black and white issue.
I have decided that I will not dither or shilly-shally in these circumstances, but make the decision and act accordingly. I listen to others input or info given, but I will not argue on the course at that time over the 95% issue. I declare the ball lost in the penalty area or lost in the general area and act accordingly.
The decision is mine to make, so I take responsibility and make it. If there are consequences at a later time, I will deal with them at that appropriate later time.
What I can't abide is other players dithering and a failure to make any decision at all or even asking others to take the responsibility in some way.