https://www.pcgamer.com/fallout-76-duped-items-are-being-removed-from-inventories/

Fallout 76 is undergoing a spot of maintenance today, with Bethesda promising to finally get rid of duped items, stripping players of their ill-gotten gains. You may return to find some of your favourite gear missing when servers come back online. 

Item duping has been an issue in the survival romp for a while, unsettling the economy and pissing off players not taking advantage of the exploit. Bethesda's been aware of it for just as long, but so far the developer has been unable to put a stop to it, despite claiming to have fixed it in previous updates.