I am not aware of any thistle canes like the one in the spoon being made by Paul Ysart. And as far as I am aware, Peter Holmes did not make thistle canes when he took over the making of "stones", in the Ysart style, for jewellery after Paul Ysart left Caithnes Glass.
After Peter Holmes left Caithness Glass in 1977 (to set up Selkirk Glass) the "stones" changed to different, and simpler, designs and with different colours - looking much "weaker" in my view. The later "stones" were certainly used in items such as spoons and thimbles.
Also, my understanding is that there were short periods of overlap in the stock of "stones" after Paul Ysart and Peter Holmes left Caithness. So it is feasible that some "stones" of the general Ysart style could have been used in the later items; however I have not seen any examples myself - and the number of spoons and thimbles I have seen is quite low.