much of science is predictions (ok im forgetting the philisophical bits for now) but it is predictions. take black holes, in reality we have no proof. does that mean they dont exist. when first thought of there was zero data on black holes. yet we thought that they existed. everything we know as proof about them is a preditction on how things would behave around them. i beleive they exist. i have no proof. i suppose that makes me unscientific? i suppose that means i also believe in fairies and unicorns?
some people did think that believing in black holes was like believing fairies and unicorns. are you a non believer? i guess that you would be because "we have no proof"
Black holes were predicted as derivatives of General Relativity. Many candidates for black holes have been found in which their effects match the predictions. Nothing to do with beliefs or fairies or unicorns.
So, the invisible and undetectable are not believed as truths throughout science.