This log shows that the update was indeed downloaded yesterday, hidden, then somehow extracted and retrieved by Microsoft. It is no longer hidden, it is no longer stored anywhere on my system, and the available free space on my drive has increased accordingly.
Huh!
2010-10-27 04:24:33:4601240
1324DnldMgr
* Call ID = {6DF447BA-0924-48ED-8A86-12A52940517A}
2010-10-27 04:24:33:4601240
1324DnldMgr
* Priority = 2, Interactive = 0, Owner is system = 1, Explicit proxy = 0, Proxy session id = -1, ServiceId = {7971F918-A847-4430-9279-4A52D1EFE18D}
2010-10-27 04:24:33:4601240
1324DnldMgr
* Updates to download = 1
2010-10-27 04:24:33:4601240
1324Agent
* Title = Update for Windows 7 for x64-based Systems (KB976902)
2010-10-27 04:24:33:4601240
1324Agent
* UpdateId = {63D6A044-8F82-4CEE-8772-0736D57F69BC}.101
2010-10-27 04:24:33:4601240
1324Agent
* Bundles 1 updates:
2010-10-27 04:24:33:4601240
1324Agent
* {517E59FA-9AC9-4852-A248-5A3F76DA4306}.101
2010-10-27 04:24:33:4601240
1324DnldMgr
*********** DnldMgr: Regulation Refresh [Sv