CRA indicates that where a drop shipment sale is not completed and the goods are bought back by the non-resident, the 1st sale can be rendered GST/HST taxable

A non-resident that does not carry on business in Canada acquired goods from a registered supplier in Canada, who retained physical possession of the goods after the acquisition. Although the non-resident had intended to export the goods for sale outside Canada, it was unable to find a buyer, and it instead sells them back to the resident supplier.

CRA indicated that a subsequent sale by the supplier of the goods generally will cause the original sale by it to the non-resident to be rendered taxable under s. 179(1)(d) unless one of the s. 179 relieving provisions applies, e.g., the new sale was an export sale described in s. 179(4).

Neal Armstrong. Summary of 27 February 2020 CBA Roundtable, Q.3 under s. 179(1)(d).