That’s more of a big plot surprise than anything else. You don’t lose any of his gear or experience, other than the muscle memory you may have built up learning his attack chains lol.

I absolutely hated it for the first 5m going in blind the first time, but then it hits almost immediately that you’ve been tossed into a survival horror scenario and you completely forget about your gear.

I forgot to make a save before entering the bunker, too, so I had to commit to it.