Never had a hope freehub fall off, and as
@Labcanary and
@beeb said they are usually well held in place by the seal. Reckon you didn't put it on right, it takes some (even) force on the green seal to actually install it properly. Hope hubs have been flawless for me, over many years.
Don't think you'll get anywhere with a warranty claim, no one is going to guarantee that you can't flat spot a rim. Spokes will lose tension at flatspots so best you can do at the moment is tension it back up and keep riding while you look for a replacement rim.
Your next step is to order you a DTSwiss FR560 or the newer FR541 rim, I'll help you build a wheel around the Hope hub.
Cheapest I can find for a FR541 rim is R2-bike, looks to be around $160 including shipping, but there is a 4-6 week wait...
Locally (within Aus) you can get a pair of FR541 from
Raild wheels for $400 plus postage. I found a listing of theirs on ebay which is $410 for two rims and postage (
https://www.ebay.com.au/itm/125594055611). I'm sure you'll find someone here on RB who would be willing to take the other rim of the pair...
You could run a EX511 rim which is enduro rated but not as tought as the freeride rims, wiggle have this in stock and cheap at $112 (add $14 postage):
https://www.wiggle.com.au/dt-swiss-ex-511-rim.
I'd be looking for the FR541 (or the older FR560) rim though, I've put an FR560 on my sons hardtail and it has held up to plenty of abuse, he is light but not a light rider
.