The inner goat of YK is for tu'mah of mikdash and kodesh where there was an awareness before becoming ta'mei but no awareness after entering the mikdash or eating kodesh. The gemara asks what the purpose of "suspending" the aveirah is. At first the gemara says that if the violator would die before bringing a knowing about the aveirah, he would get kaparah through the inner goat. But the gemara asks that if he would die, he would achieve kapara through his death? The gemara answers that it is there to suspend punishment until he knows about the aveira and can bring the korban olah v'yoreid that he is supposed to.
The gemara assumes that anyone who would die prior to realizing the aveira (at which time he would bring a korban o'lah v'yoreid) receives a full atonement upon his death. Rashi explains based on the gemara in Yoma 86a that death atones together with teshuva - just that teshua alone isn't sufficient, but complimented by death allows him to achieve kaparah. This rashi is very difficult to understand. Although it may be true that teshuva together with death achieve kaparah, but we are speaking about someone who never realized he did the aveira and therefore would definitely not have been able to do teshvua. Why does rashi assume that there was teshuva so that his death would atone, there could not possibly be teshvua without being aware of the aveira?
It seems to me that we learn from rashi a big chiddush. It is clear that even one who commits an aveira accidentally would need atonement because there was some level of negligence involved. However, unlike a person who committed an aveira wilfully, who is considered a sinner until he actually does teshuva; a person who commits an aveira accidentally is considered a ba'al teshuva immediately even before doing teshuva. BUT this only applies if as soon as the person realized they did an aveira accidentally they would do teshuva. If they procrastinate on doing teshuva after realizing the aveira, they are no longer considered a ba'al teshuva. Therefore, so long as they have not realized that the aveira was violated, they have a chezkas kashrus that as soon as they would realize, they would do teshuva and are therefore considered a ba'al teshuva immediately. Now it is understandable why they would be considered to have death with teshuva even if they would die without realizing their aveira.