Reminder -- report to S&R folks if you leave a boat in or along the river
Have the phone number for non-emergency calls to the local S&R folks handy. If you and your craft are separated, give them a courtesy call to let them know.
Give the location, type of craft, the color, and any other identifiable information. Also, ensure them that the person who was in the boat is safely out of the situation. It might also be helpful to describe if there is a possibility that the boat may float free. It is probably helpful if you have at least your phone number somehow "attached" to your boat.
Remember that if they see or get a report of a kayak all by it's lonesome, they will have to assume that the owner is somewhere in deep doo-doo and will start a search for the owner in the most logical place (the river).
A simple call might save a lot of time that these folks spend searching for someone that is not there.
City of Boulder the number is (303) 441-3333 for non-critical emergencies