Looks like there are 2 set screws holding the pin in the handle. If so are you sure there is a hole to go back into or has the hole just worn through and the pin came out but did not have to drop to do that.
I would first see if the latch set can be removed from the door and work on it on a bench. Consider a longer pin and maybe drilling deeper holes to accept the longer pin. Drilling would have to be done from the outside and would be hard to line up with the existing holes so use a small pilot drill from the outside and work your way up and file to finish on center with the original holes.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles