If a product has been de-listed incorrectly in the price file import, then a product can be left with a price but no SKU / stock code. To fix this the supplier must action the following:
Click into Price Lists on the left-hand side menu, and into Export Price Lists.
Click the Export button.
Select the All Products option from the drop-down box and click Complete Export.
Open the file and populate Column Q with the relevant stock code, save and import the file back in via Import Price Lists.