Spooky story, indeed. But first things first. Parallel universes as per many-world interpretation of quantum mechanics cannot interact with each other. So, there can be no talk about timeslip in that sense. But a more serious argument against timeslip is that the pair didn't find scorched or burning house -- they didn't find verbatim past but a property that told a story of the past (so to speak).
Another interesting fact, if I get it right, is that the message in the cement was there even after the house "vanished" (I'd be curious to know if the children footprints were still there with the rest of the message), so the tragedy was well known in the area, plus the duo was very close in their mindsets and obviously quite a lot into paranormal.
Now, before I'll continue, let me mention two similar experiences I've had.
First happened while on a vacation in a distant mountain village were our family has a cottage. It was night already and we were sitting by a campfire when we suddenly heard a somber wailing-like singing coming from the road which is c. 20 meters from where we were sitting. For whatever reason we all became scared AF, but took the courage to approach the road and saw a medieval procession of villagers all dressed in black, front row carrying icons on poles, slowly marching and singing some gloomy hymn. As we came even closer and the procession almost reached us, it suddenly disappeared into thin air. We've never investigated the history of that village, but years later we all confirmed details about our shared experience and come to consensus that it was some kind of Catholic ritual connected to plague epidemic that hit the area because of outside visitors.
Well, this prompted me to check it today -- it indeed happened in 1773. O_O
The second one happened roughly a year later. I was heavily into Castaneda at that time and had a dream about him sitting in the middle of nowhere as a huge two-faced statue of golden smiling Buddha from one side, and, from the other side, a fat guy with beer in left hand and a TV remote in the right one dressed in a greasy undershirt. He was sitting on a inverted pyramid that had enormous bowls of flower petals in each corner and these bowls were tended to by four cigar-like shaped "luminous eggs". I somehow knew it were his "witches" and, as the dream drew to an end, a fifth cigar-like ball of energy came floating to the platform. This happened before internet, so I've learned only years later that Castaneda was at that time few months after his death and four women associated with his cult have disappeared. It also happened at the time when the last of his "witches" went missing (some hikers found her skeleton in a car in the desert years later).
I must also add that in both of those cases I was high as kite on hemp (in the first case, we all were).
So, to put it all together:
1) All information from the beginning of the universe can be extracted from any spatial point in the present. All causal streams from past to present can be fully decoded, which is also why science works. (It also works for future predictions -- past and present set a general course for the future -- but predictions are, for obvious reasons, not exact). Some folks call these causal streams Akashic records.
2) We usually perceive much more than we are aware of. We can also expand our awareness to include the data that's usually out of our attention. Such expansion is possible with psychedelics, but also through meditation, etc. Moreover, some people are naturally susceptible to enter such states, particularly if they have inclination toward so-called spiritual, paranormal, etc. When people synchronize their awareness, it's not unusual to enter the same "experiential sphere" -- usual waking state is the most common case.
3) We all have our symbolic maps from which we construct our view of the world. Data which we don't understand or which does not make sense in any particular setting gets then presented as (combination of) already established symbols which we *do* understand (dilapidated house as cut out from a Twilight Zone episode; procession as seen in a movie; dead Castaneda as a beacon of truth but also a debauched fraud and dead women as balls of energy roughly like I imagined them from his books, etc.).
Thus, if I should make my guess, if an independent observer was passing on the Silver Street that day, they would probably see two young people in deep trance either just standing there or aimlessly roaming through the bushes, and then running away in panic. Which, however, does not change the fact that the siblings indeed entered and read the literal records of past for a brief moment.
