It seemed like the cop that responded was on edge, since he approached pretty fast with lights flashing, and there were 2 cops in that car. By talking about going to the ATM, maybe the dispatcher assumed I was being robbed.

Why shouldn't I call 911 for a suspected bike theft? After all, bike theft usually leads into or feeds another serious crime, in this case, drugs. And bikes aren't cheap. This wasn't calling 911 because of a power outage or a wrong order at McDonalds, this was an actual crime.