I am sorry that you were left behind that really stinks...The gate agents can indeed list you. Here's a little blurb that I have that when the gate agent gives an off line pilot grief over not listing please inform the gate agent that...

"Crewmembers May ask to be listed at the gate" !! (If traveler doesn't have access to www.id90travel.com)
-If agent says "a memo" said they can't list a jumpseater, ask to see the PNP yourself.
-If still no action or they don't know how, ask for the sup to come do it.
-If still no action, call flt ops duty phone and stress the importance of getting this done so our pilots will be able to get to work in the future.
-Note, agents should not be pressuring pilots about D-0 when the pilot is working to get the operation to run according to the book. We Should take a delay in order to do it right!
-Afterwards write up incident using ALPA website link or [email protected]