Hard to say if it's "off" or not without knowing all the facts. Was it a case of them only having x amount of spots and more senior people were sent? Or were you actively excluded? You seem to make it sound like you were purposely excluded. What are the reasons that occurred? You say your manager laughed at your request. Is that typical behavior? Are you frequently laughed at by your superiors? If that's the case it sounds like not going to a conference that has no bearing on your job is the least of your work issues.