Does TitleLeaf store a sales embargo date?

No, TitleLeaf doesn’t have a sales embargo date field in its database. As an opinionated implementation of ONIX, TitleLeaf derives a sales embargo date from the status, the preorder date, and the release date of a given product format by default:

If the status is “PC” or “PP”, then the sales embargo date is blank
If the preorder date is defined, then the sales embargo date is defined similarly
If the preorder date is not defined, then the sales embargo date is defined as the release date

This calculation can be disabled or the sales embargo date can also be offset from the preorder/release date by a number of days on request. When submitting such a request, specify the number of days prior to the preorder/release date that you’d like the sale embargo date set. Acceptable values are 0 to 180 days. This is a global setting, applying to all product formats.

See ONIX List 163: Publishing date role, value 02:

Sales embargo date: If there is an embargo on retail sales (in the market) before a certain date, the date from which the embargo is lifted and retail sales and fulfillment of pre-orders are permitted. In the absence of an embargo date, retail sales and pre-order fulfillment may begin as soon as stock is available to the retailer