OT: Job offer pulled as a result of salary negotiation

Trying to take advantage of the multitude of expertise from the users of the site, especially those in hiring positions and/or HR to see if there is any experience with this kind of thing.

Disclaimer: job is a union position with no room to negotiate advancement beyond the union-negotiated contract pay step schedule. It is possible, however, to be placed at different levels when hired.

Long story longer: I applied for a position, went though 2 rounds of interviews and was clearly the #1 candidate from the start and throughout the process. Ref. checks and Xscripts already done (no issues there). I get a call from the HR director who offers the position with the starting salary and wants 48hrs for me to respond. I am pretty content with the job I have (wasn't even looking for a new position but was asked by an acquaintance to apply to the new position). I ask about flexibility re: starting salary and she mentions that in some circumstances she could get approval but likely not in this case. She ends an email later that night reiterating the offer. I respond to the email explaining my additional years of unique experience and how I'm interested in the position but would like consideration for those additional years beyond their initial offer. I basically ask for 13-15% more than what they offered which I thought left a decent window to meet somewhere in the middle.

Maybe I was to forward/firm in the email, but HR director lady responds to me by rescinding the offer b/c they "have a deliberate recuitment and selection process and we would not want to be put in a situation or have you in a situation where you are unhappy with your employment opportunity." I was pretty shocked. At worst, I thought she'd just say,"no, we can't do that please have your decision re: the original offer by the agreed upon timeline."

Now, the main person who actually interviewed me (twice) and made the decision to select me, set up interviews, call my references, check all my documents, etc. was pretty shocked that the HR person essentially trumped her and the entire hiring process. Everything I've seen on the web, reddit, some others I know were pretty confused too. The more I think about it, I'm starting to consider it pretty unprofessional behavior on the HR director's part to rescind an offer just b/c I attempted to negotial starting salary placement, but moreso that she singlehandedly trumped the entire hiring process at this place. I mean, instead of all these questions the committee asked me across 2 rounds of interviews, they could have just cut to the chase and asked me if I'd take $XX,000 dollars with no questions asked. What a complete waste of time.

I guess my questions are, 1) any experiece with salary negotiation resulting in pulled offers of employment? 2) anyone in hiring/HR have any explanation for this? 3) any recommendation about how I should follow up?

I have no criminal history, all references were checked, called and verified prior to the HR office taking over the process. I'm kind of at a loss, but it's really no big deal b/c like I said I am pretty content with my current position. Everything I've heard/read is that you should always negotiate starting salary in a professional manner, stating the reasons for your worth to the company and your excitement for the position, which I thought is what I did. Thanks in advance for indulging in the discussion.