is there a bug when you have both the scar and scarab equipped in sp?

i notice that if i have only one of them equipped (eg scar) then when i run over scars on the ground i pick up ammo for it, but the scar stays on the ground too. same if i run over the other weapon i have equipped (eg nova). but if i have a scar and a scarab equipped then everytime i run over one of them it disappears.

you can dual equip with any wep in single player. wepons only disappear when u take all their ammo

it seems like it's still bugged then, i shouldn't be taking all their ammo if i fire one bullet, reload and then walk over it.