Actually there is some good news there. Nukes are more fragile than people realize, and especially don't do well over time. They have a number of componants that need to be fressh, and degrade fast. Nuke stockpiling is a difficult business even in the US. So just keeping a stolen nuke around for decades pretty much guarantees it's not going to be ready for prime time. Even the high explosive triggers might not work. I would guess that for this reason, if the stolen nukes weren't going to be used anytime soon, the plutonium was removed for sale on the global market, to be used in fresh nukes sometime in the future - as well as the high explosives, to be used elsewhere as well. But the original mechanisms would be tossed.
There was a Simpsons episode where the evil character had stolen a nuclear weapon. At the moment of detonation they did that freeze frame on several of the characters, just as one of the famous apocalyptic movies had so successfully done. Then they focused in on the blast and it fizzled. Lisa bends over and reads the tag which says, “Best by November 1959.”
I do understand there are some deteriorating elements, which was why nuclear testing was so important. But I’d wager we’d get some hideously dirty explosions even if they don’t work correctly. Let’s say it’s only .5 megatons instead of 5. Still pretty messy.