Though I’m not certain on this issue, isn’t there an ‘assumed grace period’ if you fully intend to go to Confession, but for circumstances outside your control are unable to? At least until the next available time you are able to receive Confession? I don’t know if I’m doing the best job of describing it, but let me try with an example (and if I’m wrong, someone please correct me!):
You live on a farm, and only one church is within reasonable driving distance (say within an hour). Confession is offered on Wednesday evenings and Saturday afternoons before the vigil. When you arrive on Wednesday, the priest on duty had been called to the hospital, so you are unable to receive Penance, even though you had every intention of doing so. My understanding is that, if something happened between Wednesday and Saturday and you died, your honest effort on Wednesday would provide absolution, because the time had not passed after that when you would next be available to receive the sacrament.
Again, I’m not really certain on this, and I don’t know of any firm (i.e. CCC) backing on this, but that is what I had always thought was the case.