That would be a communication failure: instead of taking what he said at face value for what it was, you’d be taking it as a signal. Signal-reading is the art of taking a potential non-issue and making it a huge issue.
I think that you are probably feeling one or more of several things:
– fear of inferiority
– fear of loss of love
– appreciation for the openness and honesty
What you feel is largely involuntary. How you choose to handle what you feel, though, is a choice. Some people handle negative feelings by breaking up, or attacking their S/O, or guilt-tripping, or acting out, or perhaps by contriving some betrayal in the hopes of causing pain.
Personally, my preference is to mention the feelings. This sometimes requires a leap of faith. And an assumption of best intentions (or at least, good intentions).
If you are lucky, you are with someone who repays that good faith. And the world won’t end.
a) They have to spend time together for work purpose. I am OK with them spending time together under professional circumstances. They did spend almost the entire trip doing dinner and drinks, sometimes with others, sometimes just the two of them, and an entire day to go sightseeing just the two of them. I found out about the sightseeing as it was happening. I did feel like my feeling was not being considered as we did not talk about if I would be OK with it.
b) The way he expressed his feeling was sort of in between your two scenarios. I don’t really recall how it all went down, I just remember my reaction was rage and more like WTF did you just say. And then I suggested I will just leave him to make his choice easier, that’s when he responded with: “But nothing happened because I love you.”
a) Sounds like a communication issue. I’m surprised neither of you thought to discuss them hanging out socially since they were both going to be there. That’s both your faults in my opinion, but that also means I don’t think anyone did anything wrong necessarily. Just talk about it now and make your feelings known so that going forward you both know how the other feels about it.
b) Based on your answer to a, I would say full disclosure isn’t your typical MO, so his being so open with his feelings here is a bit odd. Unless that is normal for him to be so forward with his feelings and you are just the one who doesn’t speak up (not judging, I just don’t know how you are). Either way, you should talk to him about how all of this makes you feel. Don’t point fingers or tell him how to behave, but definitely talk about how you feel and why you feel that way.