1994 Toyota Camry Cv Joint Replacement

I had both CV joints replaced last Wednesday. Car was fine until total breakdown today—while on highway, all power to drive wheels lost. (Wife driving—everything is 2nd hand to me.) The mechanic who changed the joints last week has slid under it and thinks one of the bearings may not have been seated right on the re-built CV joint, but will know for certain when he gets it apart later. He is generally known as an excellent mechanic, but nobody knows everything, so…..

Is there anything out-of-the-ordinary I should be concerned about, or possible/likely screw-up in the joint replacement, or might it simply be a bad joint? (Note: my family runs the local NAPA store that supplies the mechanic, and he has always treated us well and competently.)

Thanks.

NGX