There's also going to be a staggering amount of confirmation in the form of OSINT in a hundred different sources. If someone actually uses a nuclear weapon in anger, you will see movements around military installations you've never seen before, aircraft dispersals that simply don't happen ordinarily, etc. Even if NATO/Ukraine would be willing to cover it up or deny it for a while to prevent panic, there are just going to be a lot of tells all over the place to reflect that things got a great deal more serious. This is probably the single best thing about the folks on this site. Lots of folks who know radio, watch aircraft, pick up nuance in news reports, all that stuff. Those bells are going to be ringing like mad if that were to happen.