Sprayman, at least after this discussion you could do a little bit of detective work on your case. After the use of a grinder, there would be plenty of metal particles around the original location of your bike. If the metal was made brittle and got whacked, there might be bigger shreds left, like from breaking glass. Traces of a car jack might be harder to detect, but if your U-lock was painted there could be some pieces of peeled off paint.
I took a pretty close look and didn't find anything, which is why I think the lock may have somehow been picked. I don't know if it's true of bike locks, but it's my understanding that some other lock systems use a set number of standardized keys, so a thief can carry one of each and keep trying until he finds the one that fits into said lock.
It just occurred to me that I should run a magnet along the ground outside and see if it picks up any metal shavings. "Elementary, my dear Watson."