Trying to figure out why...

A coworker sent me on an errand during work. I had to get out the company van key, unlock the van, find and retrieve an empty plastic water bottle with no label, lock the van, and put the empty bottle inside a specific grey plastic bag hanging in the staff closet. 3 phone calls and a text were involved. I found a full bottle of Naya brand water where the empty one was supposed to be, a half full bottle on the floor at the front, and several empty bottles behind the front seats. All were the same brand. I had a feeling it was a test, and I supposedly failed. I was polite but I'm wondering _why_ he called twice from home about a cheap empty unlabelled water bottle.