Lost free space after failed Disk Utility operation?

You can resize CoreStorage Logical Volumes with the command:

diskutil cs resizeVolume lvUUID size

with lvUUID: UUID of the Logical Volume and size: a size in b, k, m ,g or t. Depending on your system version a magic size of 0g is also possible. It will expand the Logical Volume to the whole available size of the LVG.

In your case that's either

diskutil cs resizeVolume 03BC8817-F05E-4FC3-9A5C-50130CDAB3AB 0g

or

diskutil cs resizeVolume 03BC8817-F05E-4FC3-9A5C-50130CDAB3AB 2865g

If you get an error message like "... partition is too small ...", choose a slightly smaller size like 2864g or 2863g.

After a failed add volume/resize command (in your case Disk Utility froze) the innards of the Logical Volume Group are often corrupted and it has to be rebuilt from scratch which requires a (Time Machine) backup.

Adding a 2nd HFS+ volume may render your Windows partition non-bootable.