Sorry this is long!

I have been at my current work place for almost 20 months. It is in a department store in the 'food hall', basically a supermarket/grocery store.
'Lynne' got married in June. Sometimes she is very friendly and other times she doesn't seem that chatty when I speak to her, but she is always asking about my own wedding plans (non-existent but engaged for almost 3 years!) Anyway, around two months before her wedding she invited me to her hen/bachelorette party which was to be held a month before the wedding. The party arrived with no invite to the wedding. We went to a pottery painting place during the day, the plates, cups etc that we painted had to be collected another time. One of the other guests (former colleague) said that she would collect them and bring them to the wedding, I stayed quiet. That evening while we were having drinks Lynne suddenly said 'I feel so bad everyone, Wetkittennoses is the only one here not invited to the wedding, you must come!' I told her she didn't need to do that but she said I must. Someone else changed the subject.
The following week at work she asked me when I was going to get the plate that I painted. That's when I realised I definitely was not invited. I didn't show that I was hurt and said that I would check with the guest who collected them. It felt like everyone at work was invited to the wedding and talking about it afterwards. I don't understand why you would invite someone to the hen/bachelorette and not to the wedding.
It turned out that 'Colleen' the former colleague forgot to bring them to the wedding and I had been on holiday so hadn't met her yet. So, five of us went for lunch today (I was invited last weekend) and received them. It was going well and I was enjoying it. Then suddenly 'Marie' another colleague said 'now Wetkittennoses the next thing I'm going to talk about doesn't include you.' Lynne said 'that's so harsh!' While I said it was ok. She then started talking about their plans to go on holiday together next year with another former colleague and where they would stay, what they would do etc. I looked down at my plate and ate, feeling rather awkward until the topic was changed. I was dwelling on it afterwards and spoke about it to my fiance who said it is a disadvantage of being part of a friendship group later than the others, but that I should make the effort to be friends. Lynne brought thank you cards to lunch, mine had 'thank you' printed on the front and she'd written inside that she was glad I came to her party. The others had photos of them from the wedding on the front of theirs.
I don't feel there's a particular solution to my feeling left out as I think it would be even more uncomfortable to bring it up to them, but I wondered if anyone else had experienced anything similar and how they handled it? My fiance said I need a thicker skin and that I still could have joined in the holiday conversation and suggested ideas, but I didn't want to seem like I was angling for an invite!