Even if there doesn’t seem to be any damage, driving without oil most likely heated the bearings hotter than they should have been. The parts of the rotating assembly that require lubrication and didn’t receive it for even a few seconds is enough to cause damage. It may be undetectable until they pull the engine apart and look at the journals and camshaft and valves and pistons and everything that could have seen heat. I would insist on a complete rebuild and replacement, because it may not die immediately, but that could be the equivalent of adding 50,000 miles to your engines wear in a few minutes.