You missed the part where the gorilla test spawned/expanded* to real-life situations
Were the officers expecting to find a (folded) gun case made of paper, in a building with boxes wrapped in the exact same paper...
Inattentional Blindness*
@wikipedia
1 Defining criteria
1.1 Cognitive capture
2 The cognition debate: early vs. late selection of attention
2.1 Evidence for late selection
2.2 Evidence for early selection
3 Theories
3.1 Perceptual load
3.2 Inattentional amnesia
3.3 Expectation
3.4 Perceptual cycle
4 Experiments
4.1 Invisible Gorilla Test
4.2 A real-world experiment
4.3 Computer red cross experiment
4.4 Clown on a unicycle
4.5 Blindness despite fixation
4.6 Effects of expertise
5 Limitations of perception or memory?
6 Neuropsychological analogies
6.1 Visual neglect
6.2 Extinction
6.3 Inattentional agnosia
6.4 Change blindness
7 Additional factors exhibiting effects on it
7.1 Age and expertise
7.2 Similarity between stimuli
7.3 Mindfulness
8 Possible causes
8.1 Conspicuity
8.2 Mental workload and working memory
8.3 Expectation
8.4 Capacity
9 Benefits
10 Broader implications
10.1 Safety
10.2 Illusion
10.3 Police shootings
11 See also
12 Notes
13 References
14 Further reading