PROBLEM WITH CONVOYS

[frigid canopy]

Is there a way to complete the convoys if the zombie loot also disappears when they are killed?
What if they couldn't make it possible to buy or respawn those zombies with a credit card?

[serene sigil]

sometimes they respawn because of glitch, also there are i think 2 cards outside of convoys used for treasure maps but you can also use them for convoys