Review the sentence:
We looked everywhere for the car keys—under the sofa cushions, __________,
and on the counters and tabletops. All along, Andrew had them in the front
pocket of his jeans!
The blank requires a prepositional phrase. You chose searching for them in the trash can, which is a gerund phrase.
You thus have a parallelism error.
Before you continue, review the rules for parallel structure.