I didn't steal this car either
I find it rather impossible that you don't have the key then or did you lose the key?
I've never known a car in this game to use a different key for the trunk.
I've never known a car in this game to not need a key to drive it unless it's been lockpicked
I've never known a car in this game to be sold without keys when T-Ray sells them
So how did you get this car? if you bought it off another player then they either have the key or they stole it.