But I'm not sure that this is Popper's sense. I understood him to be talking about hypotheses which are so constructed that no acquisition of data would cause one to abandon them; not merely hypotheses where we are presently unable to acquire the data.
Otherwise, as I have pointed out, we would have to say that people constructing apparatus to test a hypothesis for the first time were expending their money and effort on researching a hypothesis which was not even properly constructed. People building the large hadron collider, for example, to look for the Higgs boson, were trying to investigate something which was not even a properly constructed scientific hypothesis, and wouldn't be until they turned it on, when suddenly the nature of the hypothesis would change: it would become properly constructed at the same time that the large hadron collider was.
But, as I understand Popper, it was already properly constructed: they could say what data would confirm or disprove the existence of the Higgs boson, and so they set out to acquire the data.