Scroll of Freeze dropping but not appearing in inventory

[geekgirl101]

Platform: Windows
ISP: Andrew and Arnolds
Type of Internet Connection: Fibre
Internet Connection Speed: 80MB
Date & Time: 29th November 2014 2:18am GMT
Frequency: Once (did not reproduce)
Character Name: Lumbajack
Race: Galka
World: Phoenix
Main Job: Thief 99
Support Job: Dancer
Area and Coordinates: Gustav Tunnel E-9
Party or Solo: Solo with 3x trusts
NPC Name: None
Monster Name: Doom Warlock
Steps:
Inventory was full.
Defeated a Doom Warlock.
Received the messages:
You find a revival tree root on the Doom Warlock.
Lumbajack obtains a revival tree root.
You find a scroll of Freeze on the Doom Warlock.
I did not have an existing scroll of Freeze in my bags already.
I dropped some items from my inventory to free some room which were notified in the chat log as being a couple of stacks of hecteyes eyes and a near stack of revival tree roots.
Scroll of Freeze was no longer in the treasure pool and had not appeared in the inventory.
No error message about the scroll being lost or having dropped it by accident.
GM response within 15 minutes stated that apparently the item dropped but could not be placed in the inventory for unknown reason.
Another dropped 40 mins later (3:08 GMT) and this time appeared in the inventory.