I'm trying to determine if i was in the wrong here so any feedback would be appreaciated. i attempted to book an appointment for a saturday afternoon session with a provider on a thur night but didnt' hear anything back as a confirmation so that fri afternoon a booked an appointment with another provider. Later that sat evening i found that the prev provider had emailed me back to confrim but early sat morn. ifelt bad about it and tried to reschedue and keep an open line of friendly communication but that didn't work out. In her eyes I NCNS but i didn't have any confirmation so... what are the rules of etiquette in this situation and making appointments in general?

IMHO, You did nothing wrong. Waiting until the day of the appointment to confirm, when  you made the request three days earlier, is not acceptable.

Your appointment was never set or confirmed, just a timing that didn't work out.

to be officially "ON".  A proposal without acceptance is not a agreement...  and subject to withdrawal of offer.  Since a lot of ladies just plain choose not to respond to a client they're not interested in seeing, you had no way of knowing that an acceptance would follow...  or a night alone.  

I generally try to prescreen with a lady I'm interested in & give a rough time schedule.  When she says ok, we work out a schedule.

In this situation, rather that stand on etiquette, if you are still interested...  try appologizing for the misunderstanding which she should graciously accept & agree to start over.  If she chooses not to, you have NO recourse except to move on & it'll be her loss.  
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better business practices, she probably would have sealed your date within 24 hours.  As far as I'm concerned, she is the one who lost out.  You did not NCNS.

If I find that I have some time in my work schedule to play, I try to contact a provider ASAP.  If I don't hear back within 24-36 hours (depending on how close the open window is), then I move on and contact the next lady on my list.  There have been times when I heard back after the open window had passed.  Oh well.