Copy database removed source - Cannot acces mdf file
I have never tried to use SSMS to copy a live database as you have done.  But I have copied many, many databases without an issue.

Use the following approach in the future and you will not have the same issue again.

Take a full backup (use COPY_ONLY)

Then restore the backup with a new name.  

Your live database will never be detached, so you won't have to try and figure out how reattach it