Shooting at larger creature behind the smaller creatures crowd

Question

In a recent gaming session the PCs were shooting a Medium-size slaver ghoul over the heads of Small-size kobold crowd (say, a dozen of them). The Ghoul was obviously an enemy but the kobolds were being forced into a fight and thus reluctant.

I gave the ghoul half cover due to being obscured by smaller creatures but I didn't know how to decide if a PC would have hit the kobold instead of the ghoul should they miss, thus provoking an attack from the no longer reluctant kobolds.

The PHB provides rules for degrees of cover providing bonuses to AC and saving throws only, not the chances to hit the cover. I could rule that if a PC misses by more than the AC bonus provided by the cover, then they hit the cover instead. However, the cover in this case, is a creature and has its own AC. Also, a PC can miss in any direction, by shooting over the ghoul, and not just too low, hitting the cover - so what, scatter diagram?

In actual fact, the PCs hit the ghoul, saving me from improvising, but I wonder how I should have resolved it should they have missed? In the answer, please state if the rules provided by you would apply to a situation where an archer shoots at an enemy engaged in melee combat with an ally (another case from the same session).

I've found a few answers to similar questions asked here but they pertain either to other games (Pathfinder or D&D 4e) or are about stealth not the chance to hit the target's cover.

Answer 1

There is an optional rule in the DMG about hitting other creatures that are providing cover for something, on page 272.

It says that if your attack misses due to the cover provided and the attack roll was high enough to beat the AC of the creature providing the cover, you hit the covering creature instead.

There is indeed nothing in the PHB, as there is no default rule about hitting cover.

Answer 2

You are correct that there are no rules that mentions hitting the creature or object that is giving the target cover. So, RAW it doesn't happen. If you miss and the object had cover from a creature, then you must have overcorrected to avoid hitting the covering-creature and missed both.

Remember that 5E intentionally errs on the side of simplicity. The designers have said their goal was to allow more room for DMs to make rulings on fun things over rules covering edge cases.

In my (limited) experience, really poor rolls lead to poor results. If you wanted to avoid hitting an innocent but rolled a nat 1, perhaps that poor innocent is about to wear your crossbow bolt. If instead, you narrowly missed the AC, then maybe you were skilled enough to miss the innocent but couldn't quite find the target behind it.

In short, there is nothing RAW to force a PC to hit the cover (in this case a creature) if they miss the target behind it. There is also nothing stopping the DM deciding that they DO hit the cover (even if it is a creature)