Actually we don't know what kind of "aisle" that the OP left his bike in. It could have been aisle with products that the store is selling, it could have been an unused check out lane/aisle, or it could have been a lane/aisle where the store stores it's shopping carts.

And how is it NOT comparable? Both are vehicles used both for transportation and for recreation. Both are private property, and as such the store employee has no more right to move someones car or someones bicycle, without first finding the owner and asking them to please move it.

I find it more inconsiderate for a business ANY business not to provide adequate parking for ALL types of vehicles that their customers might choose to use to in order to go to their store. And if they do not provide adequate parking for all types of vehicles then they shouldn't be surprised when someone who chooses to use a bicycle as their primary means of transportation elects to bring their bicycle into the store for safekeeping.

And if an employee decides on their own to move a customer's bicycle outside the store and said bicycle ends up getting damaged or stolen then it is both said employees AND the stores fault and both should be held accountable.