Can't Win for Losing

One of the pieces of equipment at my job failed last night right before close.  It was not an emergency issue at the time.  I alerted the opening manager this morning to the problem and told her that I would come by to try and help fix it.  The repair was beyond what we could do so we had to call the company that installed the equipment.  I waited around until the repairman showed up to find out what the cause was and how we could prevent it in the future.  Did I mention that today is my day off so I was doing all this because I wanted to, not because I had to.  The machine was repaired and all was well, I thought.  I called the store manager to let him know everything was ok.  He response was to tell me to stop working off the clock and go home.  First of all, I was not performing any duties related to my normal job function so technically I was not "working off the clock."  Secondly, I thought I was showing initiative by following through on the repair because the problem occurred during my shift.  O well. Sometimes you can't win for losing.