Last week we reported on a weird bug: NPCs in Fallout 76 had been looting the bodies of dead players in some certain events, including guns and ammo.
As a Reddit user mentioned in the forum, "Just to be safe don't use your best/rarest weapons in events like riding shotgun just in case one of the NPCs decides to steal it" because he/she only found out the best equipment went missing after they had respawned.
Fortunately, now Bethesda has published a post, stating:
"We just released a hotfix for Fallout 76 to address a rare issue where NPCs could take items from a dead player under certain circumstances. We did not need to take the game offline to do this, and the hotfix has now been applied to all worlds."
If you had encountered this problem earlier, you should download the hotfix as soon as possible. However, it seems that the lost items cannot be regained since nothing regarding this is mentioned in the said post.