Just to assuage anyone’s fears that would be beguiled into believing this nonsense.

First, nuclear weapons are not buried treasure you can just put in the ground and then dig up or detonate decades or even just years later. They are precision devices that require regular maintenance or they become inert. Most (especially from that era) would be ineffective (non-viable) after less than 18 months without replacement of their primary explosives and detonator due to degradation from radiation. None would survive more than a decade without maintenance simply due to the fact that the cores decay and need to be replaced.

Second think about this logically. If a country developed such a compact highly sophisticated device, would you really want to store it long term on the foreign soil of your primary rival where it could be discovered simply by accident any day.

No if such devices exist they are in well accessed and well known Russian embassies, consulates and related secure facilities. Not buried in someone’s random backyard like a dead dog. And even that idea is far fetched.