Urgent - SQL left join bug?

Hi, I'm running PostgreSQL 9.4.10 on CentOS 6.5. It looks like that I found
a bug with left join. It is very URGENT since it is running in the
production servers.

### Conditions: ###

I have 2 tables:

TABLE 1: (2171209 records)
\d prescription_herbs
Table "public.prescription_herbs"
Column | Type |
Modifiers
---------------------+--------------------------------+-----------------------------------------------------------------
id | integer | not null default
nextval('prescription_herbs_id_seq'::regclass)
prescription_id | integer | not null
herb_id | integer | not null
weight | integer | not null
created_at | timestamp(0) without time zone | not null
updated_at | timestamp(0) without time zone | not null
deleted_at | timestamp(0) without time zone |
price | numeric(10,5) |
special_manufacture | character varying(255) |
cost | numeric(10,5) |
pharmacy_id | integer |
Indexes:
"prescription_herbs_pkey" PRIMARY KEY, btree (id)
"prescription_herbs_hid" btree (herb_id)
"prescription_herbs_prid" btree (prescription_id)

TABLE 2: (4406 records)

\d pharmacy_herbs
Table "public.pharmacy_herbs"
Column | Type |
Modifiers
-------------+--------------------------------+-------------------------------------------------------------
id | integer | not null default
nextval('pharmacy_herbs_id_seq'::regclass)
pharmacy_id | integer |
herb_id | integer |
cost | numeric(10,5) |
price | numeric(10,5) |
no | character varying(255) |
deleted_at | timestamp(0) without time zone |
created_at | timestamp(0) without time zone | not null
updated_at | timestamp(0) without time zone | not null
name | character varying(255) |
Indexes:
"pharmacy_herbs_pkey" PRIMARY KEY, btree (id)
"pharmacy_herbs_herb_id" btree (herb_id)

### BUG: ###

I ran a SQL:
select pha.id,ph.herb_id,pha.name,ph.weight
from prescription_herbs as ph *left join* pharmacy_herbs as pha on
ph.herb_id=pha.herb_id
where ph.prescription_id=116285 and ph.deleted_at is null and
pha.deleted_at is null and pha.pharmacy_id=22 order by ph.herb_id;

Expected:

It should have 10 rows because the SQL "select * from prescription_herbs as
ph where ph.prescription_id=116285 and ph.deleted_at is null" returned 10
rows and I'm using *LEFT JOIN *in the above SQL.

Actual Result:

It returned only 9 rows and the result is the same as JOIN (not LEFT JOIN).

### More info: ###

I explain the SQL:
explain select pha.id,ph.herb_id,pha.name,ph.weight
from prescription_herbs as ph left join pharmacy_herbs as pha on
ph.herb_id=pha.herb_id
where ph.prescription_id=116285 and ph.deleted_at is null and
pha.deleted_at is null and pha.pharmacy_id=22 order by ph.herb_id;

I got:

Sort (cost=131.73..131.76 rows=10 width=24)
Sort Key: ph.herb_id
-> * Hash Join* (cost=122.02..131.56 rows=10 width=24)
Hash Cond: (ph.herb_id = pha.herb_id)
-> Index Scan using prescription_herbs_prid on prescription_herbs
ph (cost=0.43..9.68 rows=23 width=8)
Index Cond: (prescription_id = 116285)
Filter: (deleted_at IS NULL)
-> Hash (cost=113.08..113.08 rows=681 width=20)
-> Seq Scan on pharmacy_herbs pha (cost=0.00..113.08
rows=681 width=20)
Filter: ((deleted_at IS NULL) AND (pharmacy_id = 22))

I think the above* "Hash Join" SHOULD BE "Hash Left Join"*, right?

I tried to explain another SQL:
explain select * from doctors d left join prescriptions p on d.id
=p.doctor_id;

I got:
Hash Right Join (cost=2159.33..31453.58 rows=130330 width=2936)
Hash Cond: (p.doctor_id = d.id)
-> Seq Scan on prescriptions p (cost=0.00..9273.30 rows=130330
width=495)
-> Hash (cost=576.37..576.37 rows=5037 width=2441)
-> Seq Scan on doctors d (cost=0.00..576.37 rows=5037 width=2441)

The "Hash Right Join" is the correct node.

Any help is very appreciated! WAITING...

Thanks,
Kaijiang