Well it has happened to me quite recently.
I am new to being poly and still learning the ropes. My girlfriend was also quite new to poly as well. We both were learning how to set healthy boundaries and respect each others boundaries while learning about open and honest active listening.
Then she wanted to ride home with someone I did not trust from a prior meeting with him. Well the repercussions of my concern were treated as if it was pure jealousy. I rode home with them and had a delightful and insightful conversation that gave me a new perspective and opened up my eyes, but all my ex could see was that I was infringing on her boundaries, while she did not respect mine.
Well when we got to a mutual friends house, things seemed fine till I addressed concerns about how I felt things should have been done a little differently. Well then it was like a nuclear bomb went off for her for me suggesting that and she left.
The next day things seemed to be back to normal and we talked about the things we had learned and I was hopeful I could surprise her with a ring at the fair; however she moved in to the mutual friends house and was planning on dumping me rather than to discuss how she was feeling and address the solutions I was already working on. Not knowing she was getting solace from these married friends of mine, I asked for solace myself.
I got none and I was treated as if I was trying to put them in the middle of a domestic issue (which was not the case).
I respected my girlfriends boundaries, but was actively talking to any friend I could find for comfort and advice. However, my exes mom called and was worried sick about her and was providing me comfort. I come to find out, that comfort and solace were no longer what they were looking for, they were now a triad, my ex was the secondary and unicorn, and she did not need me and they did not want me. My Ex has since been rude and brash about her feelings, which I feel was disrespectful as I felt she ran away rather than try to understand why I reacted the way I did. They disrespected me in not being friends to me when I needed it, and becoming involved with her the same day she officially broke it off.
Only the wife feels like she needs to apologize and remain my friend in all this, claiming I am 100% right in that we all should have talked this all out (as I would have trusted them as her play partners and such if she asked.)and respected my feelings as well as helped us both. I feel like my boundaries were as disrespected as the ones that they originally felt I was breaking. I feel as though not only did I lose the love of my life, but my so-called best friends as well. I am torn whether to accept the wife's offer of a sit down to share feelings, as it is too late to repair the damage caused by all parties.
On a positive note I hope they are happy as I feel they are good for each other;however, they lost a good friend, and my ex lost a good man.