This site is still a work in progress.
This is a bug that happens.
When you first buy a car it should spawn in parking lot of where you bought it. If for whatever reason it didn’t then you can try check Alta garage.
It’s more likely that the garage will say the “vehicle is out” This meaning you will not get the vehicle until the server restarts or you've been off the server for over 6 hours.
If this is the case it and you have no other vehicle to use, it may be useful to hire a taxi, get a taxi or get someone to drive you around.