I sent a train hauling cars in 1941 to the depot. When I clicked on the cartrucks, they disappeared. The number of stored vehicles increased accordingly, but no cartrucks appear in the vehicle list, not even with "Show all" active.
P.S: I just noticed that the only car dealer in the country has gone bankrupt; that's probably when the trucks disappeared. It's confusing if you are not aware of that mechanism. Perhaps a notice in the event list would help?
The car dealer closing would be the reason that the cartrucks were not available, if you had "relevant" rather than "all" selected in the types of freight vehicles to show.