I lost the source code from one project I did on the company I'm working for and haven't been able to find a vb6 decompiler, does that even exists?
Forgot to say that I only have the EXE. I completely forgot about this project and rescued the EXE from a user's machine.
http://www.program-transformation.org/Transform/VisualBasicDecompilers
This link provides a lot of resources for VB6 Decompiling, but it seems like it will depend greatly on what you DO have (do you still have the pre-link Object code [EDIT: er... p-code I mean], or just the EXE?) Either way, it looks like there's something, take a look in there.
For the final, compiled code of your application, the short answer is “no”. Different tools are able to extract different information from the code (e.g. the forms setups) and there are P code decompilers (see Edgar's excellent link for such tools). However, up to this day, there is no decompiler for native code. I'm not aware of anything similar for other high-level languages either.