EDIT: According to the changelog of the latest patch, this is fixed, so this is obsolete.

After playing with the 2017 April Fools update, your weapons will still have ricochet ammo equipped, even though it was removed from the game. The game's procedure to clean up invalid weapons notices it has a mod not in the allowed list and flags it for removal, however since the mod is no longer in the parts map, it can't determine what type of mod it is to check if there's a default it should apply, so gets rid of the weapon altogether. There's also a few other places where it can fail during cleanup, such as trying to add the mod back to the amount available while selling the weapon. This mod adds a seperate check for the ricochet ammo and flags it for removing just the ammo instead of the whole weapon, and changes other needed procedures to allow it to remove it.

If you've been playing the game since losing your weapons this won't get them back, but if you haven't played since before the April 3rd update this will keep you from losing them.

Unzip into your BLT mods folder.
Start the game.
Make the game save your character(switch equipped weapon or mask or something).
Exit the game.
Remove the mod.
Your weapons should now all be normal and you won't lose them.