Remove adapter from hose Y connector
I'll bet the part on the left looks like the part on the right. One can see the bearing surface on the left which contacts the ball valve. Comparing it to the right side, it appears that the insert is threaded and was unscrewed rather than the desired hex item. Consider to apply a bit of thread locker to the external threads on the item on the left, taking care to restrict it to those threads, or apply thread locker to the internal threads on the left side, without getting any on the ball assembly.
As you should never need to open that section again, red (permanent) thread locker may be a good choice. Blue (temporary) thread lock could break free. After allowing the assembly to cure for an appropriate time (read and follow all label directions), you should be able to remove the hex item as originally desired.