I see no reason to blame the tech who did the alignment and lower control arm. If you must draw conclusions, I must say that the person who installed the upper control arm is the logical choice.
As a technician I find it very interesting that you tend to blame the last person you saw rather than the obvious installer of said loose part.
You can't imagine the stereotype customers this brings to mind.
Bosch Master, ASE Master, L1
33 years MB technician