That definition, by its very nature makes it impossible for one to know if the proof is a sighting.
Agreed, I see your point. However, one need not have these experiences alone. I won't say any more about it, because it will cross into the old philosophical argument about how we can't prove each others existence.
Can I prove that you exist? If I have others confirm it, do they really exist? and so on
At some point, as you have experiences, as others confirm them or experience the same thing, you make up your mind as to whether they are delusions or not. If you are objective, and learn your own mind, and are honest with yourself, you should be able to trust yourself. Or end up in a padded cell, but then the padded cell might itself be an illusion.
Either way, God or no God, receptor for energetic communication or result of evolutionary need for God, in the long run it doesn't matter.
If you search and become comfortable with your "spirituality" and it makes you happy, great. If you decide that it's not worth the trouble and become an atheist, great. The outcome is the same either way, we die. If there is a God, it is impossible to tell what s/he wants from us, no rules. If there is no God it doesn't matter how you live your life, again no rules.
No good, no bad. Those are human constructs.