I mean how would you explain it if they would find something?

I guess this is another Bayesian vs classical statistics thing. In Bayesian thinking, absence of evidence is evidence (not proof, mind you, but it is information).

Sure, it's information. Thing is you have no idea how informative it is, because then you would have to know how likely it would have been that some time traveler would make one of the two particular search queries they tested. Since we know absolutely nothing about time travelers, I think the information content is negligible.