It is possible the shop may have installed the ring and it fell off. I had that happen on one of my troopers, and the end of the axle was all ground up like on yours. Being as cheap as I am I just took a hacksaw blade and ground in a new snap ring groove. I then went with a slightly smaller snap ring. Not the best solution, but it has held up for about 3 years so far.

Jay <img src="/forums/images/graemlins/mrt.gif" alt="" />

1989 Trooper 2.8 V6 5-Speed(the daily driver)- Superwinch Hubs, otherwise Stock - $350
1990 Trooper LS 2.8 V6 Auto - Superwinch Hubs, otherwise stock....for now - $182.50
1983 Chevy Blazer - Stock - $150
No Car Payments - PRICELESS