You said 'map' so I assume you mean Region deliveries. Your stuck delivery truck is likely stuck behind traffic in the region. This often occurs when delivering resources to the Great Work or a Global Market delivery. Playing on Cheetah speed while watching your truck from your city drive thru the Region then hit traffic definitely looks like it's stuck.
You can switch to Region view, select the Freight icon, and advance the game speed to Cheetah speed. This will highlight the delivery trucks on the region highways, allow you to vaguely see the traffic (especially if you focus on a city near the truck in question), and the speed will allow the traffic to clear faster and your truck will get closer to it's destination, showing that it's not actually stuck.
If the truck is making a neighbor gift delivery to your city, the truck will not even appear on your Region highway if the truck gets "stalled at the border" as reported by the game through a notification at the top of the screen. This will continue until you resolve the cause of the stall in the receiving city.
I've never seen a stuck delivery truck in the city (except what is caused by the Pause game button) especially in version 10.3. City buses will stack up inside each other at popular bus stops and delivery trucks will stack at the Trade Depot or Trade Port pick-up/drop-off point. However, this stacking doesn't hinder the vehicle's ability to depart at the appropriate time.