The Wild Cards are the default loot. If the loot chance rolls “you don’t win the unique loot” and you already have ten Wild Cards (which is the maximum amount), Dr. Boom’s corpse will not be able to be looted.
That’s not to say that there isn’t a bug with having no loot drop, however for most players the situation I described above is working as intended. (If one were to argue it’s stupid game design, yes I agree.)