For most contractual agreements you assign copy-write of your work to your employer. So if you used your personal project in work for your employer the copy-wri

For most contractual agreements you assign copy-write of your work to your employer. So if you used your personal project in work for your employer the copy-write becomes theirs. My guess is that in your hypothetical scenario the first company would own the IP and could sue the worker or other company for infringement.