Loss of no claims is not guaranteed. If you are insured by Direct Line they have a fair claims commitment where you don't lose no claims even if they cannot recover money from anybody. They list these circumstances and I'd be surprised if hail didn't come under either flood or debris.
- Hit whilst parked
- Potholes or poor road maintenance
- Theft of the car, or from the car
- Flood damage
- If you hit or are hit by a wild/domestic animal
- Hit by an object or debris (excluding vehicles)
If you're not insured by Direct Line they loss of no claims is likely unless you have protected it.