I can’t see how this can go against you, he already TWOK the car once then like you say hid the keys in the garden, it’s a shame the police didn’t stake the car out upon the guys release from custody as they could’ve then nicked him again.
The police were aware the keys were in the garden did they not advise you what to do at the time? If not then they’re as culpable as they should’ve really suggested what to do.
If you have legal cover kn your home insurance you could always call the hotline for advise but I think until the insurers come back to you there’s not much you can do. Just think very carefully how you tell them what happened, I don’t mean lie of course but ensure you don’t leave them reason to assume anything like obviously don’t say something like I threw the keys at him & I’d also ensure they’re aware of the state you were in medically (Dr’s letter possibly) & whether you felt in danger if you fought to get the keys back etc.
If you felt in fear of being assaulted or worse then tell them that, again don’t lie.
If you haven’t already get it all written down with dates & times & as much detail as you can muster that way if they do decide against you you’re all ready to get it straight to the ombudsman.
Good luck with it all I’m so sorry you’re going thru all this it’s the last thing amyone needs when ill