Type of Internet Connection:
DSL

Date & Time:
23/06/2015 about 19.00 and 23.45 CEST

Frequency:
Noticed twice but assume its a general bug


Character Name:
Own Character: Aelia Sokoto - Noticed on: Vintent Sable / Random DutyFinder Whitemage

World:
Cerberus - Instance servers for Sohm Al and Castrum meridianum

Class/Level:
Own: Scholar 53/54
Others: Monk 55 / Whitemage 52

Party or Solo:
Party (Light Party, Full Party according to instance)

Steps:
1. Person has a disconnect
2. Person reconnects you notice that the buffs like Stoneskin and Protect vanished

As I hadn't seen buffs vanish upon disconnect since maybe 2.1 I assume this is a bug implemented in the latest patches.