Hi Hudar,
Excuse me for late response.
Recently, TARGET_SPEND has just been made to be able to use as in the
standard context as well (see
guide).
For a standard strategy, biddingStrategyId is not returned, as expected.
So, could you please confirm if you set up your bid as the portfolio or standard context?
If you're sure that your bid was set up in the portfolio context, could you please send me more information, e.g., your client customer ID, campaign ID and the most recent SOAP log showing that the bidding strategy ID wasn't returned?
Please note that v201506 is already deprecated and will be sunset within 7 days from now.
I highly recommend you to upgrade to v201603 as soon as possible.
Cheers,
Thanet, AdWords API Team