Happy cake day!
Hmmmmmmm… Pretty tough with the small description, you might be the only one who can come up with the exact perfect title.
If I can’t think of a title that describes the entire story, I come up with a title that describes a metaphor that describes the story.
For example...
…if I was writing a story about a summer romance between a positive girl and a guy with a troubled past, and there was a scene that showed them looking at tide pools, with her saying: “Look at these fish trapped in the tide pool. Their world must feel so small. But soon, the tide will come in, and the whole ocean will open up to them.” I might call that story Tide Pools.
So for your story, idk, maybe they have a serious chat about how she suppresses her emotions in favour of facts and numbers. Maybe she chews him out for not keeping his car secure, and it turns into how she keeps her heart too secure. You can turn your focus into making a title that alludes to those scenes. 
Just throwing out a few other ideas:
Cybersecurity
Encryption
Encrypted Heart
Or anything related to cool hacker terms that I don’t know; I’m not entirely sure how a hacker would find a car thief lmao.