Ogre Geargrabber

The delayed triggered ability (“When you lose control of that Equipment, unattach it”) triggers the next time you lose control of the Equipment for any reason, not just when Ogre Geargrabber’s control-changing effect ends. The Equipment will become unattached from whatever creature it happens to be attached to at that time. It doesn’t matter if Ogre Geargrabber is still on the battlefield at this time.

If the targeted Equipment can’t be attached to Ogre Geargrabber for some reason, you’ll still gain control of it until end of turn.

Any ability of the targeted Equipment that triggers “whenever equipped creature attacks” won’t trigger. That’s because Ogre Geargrabber is already attacking at the time that Equipment becomes attached to it.