Not quite true: the best resolution you're going to get will be about six inches, which means that you can distinguish the PRESENCE of a six-inch square object, not identify what it is.
I'll admit to not having much knowledge about them, that's why I asked the question aloud, hoping someone with better knowledge could address whether some sort of surveillance telescope (satellite, U-2, etc.) could have examined the Columbia from afar.
U-2 is out--the cameras point the wrong way (don't even THINK of trying to roll a U-2 inverted).
Satellites--orbital mechanics may have precluded a detailed examination (you need the satellite, the Shuttle, and the Sun to all be in proper relationship with each other in order to examine the wing in detail.
Additionally, there is the possibility that the object striking the left wing did NOT do significant damage, and that any damage to the tiles was done while in orbit. (IIRC, one of the Shuttles took a window strike on orbit a few years ago--had the same object grazed the underside TPS instead of a window, it would have taken out several tiles, and in all likelihood no one on the Shuttle would have known until reentry.)