I don't believe it is built yet either. Did you hear a call for them? What part of the district. Littleton was planning a station #19 near Chatfield Greens, but I don't know that they've even started on it.
I saw Engine 19 today at Jeff Dunn's funeral (Castle Rock Firefighter/Paramedic who died of ALS). It's probably just a reserve unit that is only put into service for special events or when they need more coverage in their district. I believe that is what Medic 10 is also used for.
Keep Jeff and his family in your thought's and prayers. May he rest in peace.