To the OP's question.... No, I have seen no proof of it in scripture.
There are no specific passages that I know of that cover this topic.
There ARE a LOT of scriptures that explain the love that God has for all of His children, and the forgiveness that is there for all believers. The example Jesus gave of the prodigal son.. the fact that the apostle Paul had been responsible for the death of many Christians before his salvation... King David had one of his best soldiers killed so that he could take his wife. Moses murdered an Egyptian...
So, murder is not an unforgivable sin, if we are covered by the blood of Jesus
And, I would not categorize suicide as "murder" anyway... it is the result of a mental/emotional imbalance, or sickness, because all experts say that the strongest "natural" instinct we have is the instinct of survival. To bypass or overlook that instinct would take a mental illness of some sort.
If doing this is on your mind, I pray fervently that you will find someone to counsel with you, prayerfully, and help you work through whatever issues you face.
If you are wondering about a loved one, then I think you need to remember the unbelievable level of love that God has for us, and the unlimited forgiveness He offers us through Jesus...and rest in the knowledge that your loved one is going to stand before a loving father, who wants nothing but the best for his children...