The Old Sogdian script is not yet in Unicode. The script has a tentative allocation at U+10F00..U+10F2F in the Roadmap to the SMP for the Unicode Standard.
A number of proposals for its inclusion has been submitted to the Unicode Technical Committee and WG2:
2015-11-03 Preliminary Proposal to Encode the Old Sogdian Script in Unicode — Anshuman Pandey ( L2/15-089)
UTC #146 Minutes ( L2/16-004) (See D.4 for decision and action items)
2016-12-31 Proposal to encode the Old Sogdian script in Unicode — Anshuman Pandey ( L2/16-312)