Traveler's Backpack can be deleted by Ender Dragons, which also does not cause them to drop their contents. (Perhaps qualifies as a bug due to arguably unexpected item deletion, but Ender Dragons destroying blocks is technically expected behavior). This is frustrating, since they drop as a block separately from the grave on death.

Thank you for the report.
Please, check Travenelr's Backpacks issue tracker - maybe this suggestion was already made to the mod autor?