From the most recent
BRB FAQ (
http://www.games-workshop.com/MEDIA_CustomProductCatalog/m3170233a_40K_RULEBOOK_v1.4_APRIL13.pdf)
Page 131 – The Relic, Dropping the Relic
Change the second sentence of the first paragraph to “If the
model falls back, the Relic is dropped automatically before
the model performs its Fall Back move. If the model is
removed as a casualty, or is in any other way removed from
the table – whether voluntarily or otherwise – the Relic is
dropped automatically and placed within 1” of the spot
where the model last was before it left the table. Note that
embarking onto a Transport is an exception to this, as
detailed below.”
Thus, when you remove Oby and his unit from the table, he'd drop the Relic.