We are all humans and appreciations are rewards that gladdens anyone. Some developers live a totally normal life. Especially those that have grown to build a family and have to keep them with love. On the other hand, there are a lot more melancholic developers that only find peace by dealing with complex logic.
If a developer contributes to your project, start-up, firm, it shouldn’t matter if they are still contributing or not. In cases of open source projects contributions, even if you didn’t accept their pull requests and didn’t take their changes, the attempt is worth appreciating. See what Brian Okken says about it: Power of thank you