Session opened on replica doesn't see concurrently created indexes at this time on master.
As I get, on standby index is visible when you run SQL queries on catalog tables (that is what \d+ does), but planner doesn't pick it. Assuming that in new session planner picks this index, it seems to be bug for me.
------ Alexander Korotkov Postgres Professional: http://www.postgrespro.com The Russian Postgres Company