Hope 5 pro hub cassette mount fallen off hub body on the first ride

To keep it short – patient is brand new Hope Pro 5 hub with XDR cassette drum. Wheels were built and hubs were serviced by a reputable shop on the other end of the country. Everything was supposed to be ready to ride.

I've mounted a cassette following Sram XDR manual. On the work stand everything was fine.

10km into the shakedown ride I've started to get bad shifting. Another 5 km or so later I've lost power and cassette started to turn both forward and backward without much resistance. At this point rapid uncontrolled disassembly of supposedly quality Hope hub was not yet apparent

I've started my walk of shame home and after few minutes pedals has started to turn as I walked my bike forward at this point I've noticed exposed freewheel pawls and blue grease inside of the hub.

Questions:

1. can this be fixed? Can you give me any pointers how?
2. Have my cassette and wheel install done this or the shop has messed up?
3. how to prevent this from happening again? I got lucky riding close to home. My typical trips are into the woods far from potential help.

EDIT – Stuff I've verified:

1. all parts that are supposed to be mounted according to hub exploded view and XD/XDR freehub exploded view are there
2. I've removed cassette and disc rotor and measured OLD – Over Lock-nut Dimension to 148mm which is correct for my 148mm drops
3. My hub dropouts measure to 149mm OLD which I guess is ok
4. hub body says 148mm, freehub locking plate says XDR which is correct

EDIT 2: I've put everything back together but I still want to understand what is going on since it's just going to fail again if the fault is not addressed.