Time being relative and all try this maybe... As you approach the speed of light time slows down. What if events have a momentum? The more energy behind said event (war, house fire, etc) the more momentum. If a past event had sufficient momentum it could happen slowly enough compared local space time to pass through our accepted reality in an observable way? This is a huge stretch, but I'm sure it could be made to work.

Perhaps like that, or possibly something related to light/energy from stars? The light we see from some stars can be up to 40+ years old- light created back then. I wonder if something could be built up from there?

I can't imagine anything coming from that. You would need a mirror effect, and there is nothing to provide said effect. Light doesn't just hang around like that.