This is so frustrating moment. I am sorry for you, I experienced it too but not a private key in etherium wallet but in the help of the project team I recover it. At that moment I am really frustrated I research all of the possible way that I can try but ot does not work and the last thing I do was to ask for the help of the team and luckily they helped me. Since then I am very careful and have a back ups of my private key, hopefully you will do it. Lesson learned so next time it could not happen again.