This question is related to a SE:WB question of mine. I shelved the project about a year ago and am now dusting it off. To sum the concept up: several hundred million years ago a rather impenetrable barrier was erected by an unknown actor to encase the Solar System; extrasolar objects may enter the cordoned volume, which spans a couple dozen thousand AUs in diameter, but anything attempting to leave is quietly voided. (This means that objects that are "deleted" produce no emissions as a result of deletion.)
I imagine that in the near future, perhaps in the 2060s, we'll get some real cosmic shots off, shooting away perhaps a thousand small nanocraft probes to a nearby candidate solar system, probably Proxima b, more or less as the Breakthrough Initiative envisions it. (As of yet, the team leading the initiative finds no "dealbreakers" in the concept; however, there remain challenges to be overcome.) Ultimately, the effort will fail as the ultra-velocity spacecraft ghost into the night, and we won't have any good idea why--or will we? This is essentially my dilemma. Could we explain the disappearances without invoking an alien presence? Or would the evidence against any unexpected nature of the interstellar medium/design flaw be too damning? Given the likely mission objectives of Starshot, what evidence could there even be?
(Let's work with the Breakthrough Initiative concept proposal linked above, assuming their listed hinderences have been nominally surpassed and following their proposed target and mission objectives.)
Knowing this will help me develop the, um, psychology of future space explorers/colonizers. Currently, I'm thinking that if the failure could be reasonably explained away without much woo-woo, I can put off/suppress the launch of further interstellar Starshot missions for the deployment of sophisticated space-based observatories and telescopes perhaps capable of directly-imaging exoplanet features, in effect making Starshot temporarily "obsolete" or out-competed. The Starshot arrays could then be relegated to intrasolar missions--at least for a while.
If the failure can't be rationalized without giving people shivers, I will have to follow a different chain of events that thus alters the worldbuilding. After enough of Starshot attempts, it will become quite clear to people that something out there is seriously suspect. If, however, I can put off future attempts as mentioned previously, then I can allow space-based infrastructure to develop under a more hopeful and optimistic mindset. If not, then I expect an attitude of near-nihilism or a nonbelief in the infinite potential of humanity--and an uptick in the Lovecraftian horror genres.
I don't expect the effect to be so great to produce super-radically different futures, but I do expect there to be a psychological difference among people should they learn this higher truth early on in spaceborne development.