Event 11 picks the "sprite" that was clicked on and if the cows variable = 0 on that tick then in your actions you try to spawn a red stoplight and add that as a child to the picked "sprite". You can't add a child when it hasn't been created yet, so swap those two actions around.
In Event 12 you are trying to pick a different "sprite", based on UID however you have already picked a single sprite (the one you have clicked on). So unless those two sprites end up being the same you will never pick the one with the UID. That would mean that anything after that top level condition wouldn't run.
Hard to suggest an alternative cause I can't see what you are trying to achieve in context. Upload your project file via dropbox etc. if you want any more help.