[whpalmer4]

Once you've made changes on a device, don't use OmniFocus on any other device until you've successfully synced the one where you made the changes.

Good news: they've said they plan to fix problem this after they finish rewriting the user interface for OmniFocus for Mac. Having the new shiny sooner outweighs an occasional bit of data corruption, right?

You may want to set the preference to back up every time you quit OmniFocus, and get in the habit of quitting (or explicitly doing an OmniFocus backup from the File menu) after doing a big block of work. Had you done so, you could have restored from your last OmniFocus backup on the Mac and gotten your work back, though it would still be an inconvenience to retrieve the new items added on the iPhone.

Apparently, the bug you encountered is only seen when items in the Inbox are processed. Perhaps someone in the know at Omni could comment on whether moving everything in the Inbox en masse to a project ("Fake Inbox") and syncing would eliminate the vulnerability. If so, you could do that before getting on the plane or otherwise leaving your Internet connectivity behind and still be able to spend the time offline in a productive fashion.

A final word of warning about some sync behavior that is unlikely to change even when the Inbox issue is fixed: if you change the same item on two different devices without syncing in between the changes, you risk losing the first change made, or duplicating the item if the change made was completing a repeating item. For this reason, OmniFocus isn't reliably used as groupware where anyone can change anything at any time.

If you always sync a device before and after using it, these issues go away, and sync performance generally improves, too.