I think, as you have discovered, that you may have been mistaken. I cannot even think of a mechanism within the COSPAS-SARSAT system by which this could be accomplished.

Now, having said all that, The U.S. online beacon registration system does allow you to easily insert useful information in the "Additional Information" field and I encourage users to put their itinerary in this field, or a link to it elsewhere online. This is an excellent way to assist SAR.