Who owns song copyrights when owner become defunct?

I wrote a “song poem” called The Key Is Still there,in 1977,and assigned it to MSR (George Liberace) Music. But that now-infamous
company became defunct,with no successor. Did the song copyright
revert to me?
I must make this clear: Once again,
MSR Records has NO successor. It’s
COMPLETELY defunct as far as I know.
Which means that MSR has NO successor.