SQL & PL/SQL

I'm trying to fix an order for customer manually, but our software uses hibernate to generate a random OID for each record, so I made up a sql statement like this:

update orderTable set orderSubTable1ID =
(insert into orderSubTable1 (orderSubTable1ID)
values (hibernate_sequence.nextval)
returning orderSubTable1ID)
where orderTableID = 123456;

orderSubTable1ID is a column that exists in both orderTable and orderSubTable1, so it functions like a FK. Whenever a record is generated in orderTable, an order
is also generated in orderSubTable1 and its ID inserted back into orderTable.
However, once in a while (the order I'm fixing) a record is not created in orderSubTable1, so I need to manually insert a record and put back its OID into orderTable.

The above sql gave me this error msg:
ORA-00925: missing INTO keyword
the * is pointing at the returning clause.

My colleague suggests the following:
Step 1:
select hibernate_sequence.nextval from dual;
Step 2:
insert into orderSubTable1 (orderSubTable1ID,....) values
(result from Step 1, ......);
Step 3:
update orderTable set orderSubTable1ID = [result from Step 1]
where orderTableID = 123456;

I'm not sure if the delay between Step 1 and Step 3 would cause any problems or not, and would like to have this task integrated into 1 statement. Anyone has idea how to do it? Many thanks.