I think that you are saying that an IRS form 1099-B transaction where basis was reported to the IRS is not being displayed on an IRS form 8949.
The instructions on the IRS form 8949 Sales and Other Dispositions of Capital Assets states:
Note:
You may aggregate all short-term transactions reported on Form(s) 1099-B showing basis was reported to the IRS and for which no adjustments or codes are required. Enter the totals directly on Schedule D, line 1a; you are not required to report these transactions on Form 8949.
Does this explain why your entry is not found on the IRS form 8949?