Ran into a situation in a single player 1.7.10 game using gravestone 2.15.0 where a gravestone was not created as I "had no drops", and yet I was wearing enchanted iron armor, using an enchanted iron sword, had a stack of torches, and a bunch of food. Had to restore my inventory using the /ob_inventory command. The restore worked correctly, so gravestone must have known I had items.

[08:33:52] [Server thread/INFO] [OpenMods/]: openblocks.common.PlayerInventoryStore.onPlayerDeath(PlayerInventoryStore.java:303): Storing post-mortem inventory into C:\Users\Administrator\AppData\Roaming.minecraft\saves\Ooo\data\inventory-Thoggami-2015-11-07_08.33.52-death-0.dat. It can be restored with command '/ob_inventory restore Thoggami Thoggami-2015-11-07_08.33.52-death-0'
[08:33:52] [Server thread/WARN] [OpenMods/]: openblocks.common.PlayerDeathHandler.onPlayerDrops(PlayerDeathHandler.java:338): No drops from player 'EntityPlayerMP['Thoggami'/488, l='Ooo', x=-360.32, y=71.00, z=45.93], grave will not be spawned'

Sorry, but this is wrong place for this bug report. You are using graves from openblocks mod not gravestone mod, so this is not my bug)) Post it here https://github.com/OpenMods/OpenBlocks