Here's the reality check: The miscreant got a copy of his source code. Source code consists of the actual text, and the copyright. The miscreants have an _illegal_ copy of his source code, that is a copy without any rights. The company itself has (probably several) copies of the source code, and they have the copyright. In my case, source code for my apps in the app store is on git hub, on Mac #1, on Mac #2, on the backup of Mac #1, and on both backups of Mac #2. That's not just source code, but also full revision history. So even if they copied the code from GitHub, destroyed the repository there, and destroyed one Mac with all its backups, I would still have at least two copies with the full version history.
What can they do with the source code? They can publish it. And then someone tries to use it and release an app on the app store. And then I send a DMCA notice to Apple, and the app is gone within two seconds, and at the same time I call the lawyers. Nobody in that situation would send any ransom, instead I would hope and pray that some idiot is stupid enough to use the code and get his arse sued of.