Apart from it being against CV restrictions it sounds like your friends are a pretty immature group. The way I was brought up it was pretty bad manners to organize a group event but just leave one person out. I would never have done it but some people are ignorant.
This happened to me in one workplace. A woman (Ill call her Glenys) was having a flat warming party and asked everybody except me! Thing was, I had worked with her a few years earlier and invited her to my night out for my birthday. However in the intervening years I had taken professional qualifications whereas Glenys had never taken exams and had not moved on in the professional sense. Technically I was now her senior so there was obviously some jealousy there.
I decided to teach Glenys a lesson in manners so I turned up on her doorstep with two other workmates and a bottle of wine. What could she say? "You were not invited" in front of everyone? I know I spoiled the evening for her. I even proposed a toast to her new home and wished her every happiness. Her face was like a mask!
I was longing for her to challenge me as I had a little speech made up about it being a "misunderstanding" and assuming it to be "a general invitation as leaving one person out was considered very rude in the circles where I grew up." However she said nothing.
The following week was my last as I was returning to my full time exams course. I arranged a night out with drinks followed by a club. I made a point of inviting a group of people, of whom Glenys was one. I announced that those who did not fancy the club were still welcome to join us for drinks.
"I arranged it that way so there is something for everyone as I dont believe in leaving people out. Thats not what we do where I came from."
Glenys turned on her heel and walked off to puzzled glances from her co-workers. Needless to say she did not come to the night out, even though she was invited. I never saw her after |I left that department.