Origins Easter egg: Maxis drone did not drop after killing the pilot

[SilenceMonkey]

i was doing the easter egg with a friend and we where at the point of killing the pilot.
Without a doubt did i shoot him down, i saw him falling from the sky.
after that i used claymore's and i saw it explode without a visible. we even had a couple Nukes/Kaboom.

after using 2 or 3 zombie bloods the zombie was no where to be seen, but the maxis drone didn't drop.
we even looked for the drone using zombie blood (on some site it said that: if you kill the zombie without seeing it, it could bug out and be only visible in zombie blood).
after spending 9 zombie bloods looking for the drone and/or the zombie, we just gave up.

was our game bugged or was there something that i missed?