I read through the entire thread and since I don't know the entire situation from both perspectives, I'll stay out of the issues at hand.
However, I did want to ask re: the conjunctivitis. If I'm not mistaken, conjunctivitis is pinkeye and is highly contagious. When during the week was your daughter out sick? Has she been back to school since? If not, did you touch base with the troop to assure them that she was still going on the trip? As a parent, it's easy to assume that the troop leaders will check with you if they have questions about your child. As a troop leader, however, I can tell you that it's a true feat to keep up with everything. As others have mentioned in this thread, troop leaders are (often unappreciated) volunteers. I am extremely fortunate to have a wonderfully involved, caring group of parents involved with our troop this year. That's not always the case, though, so I would give the leaders the benefit of doubt if possible.
Now, having said all that, if you truly believe that the leaders deliberately left your daughter, chalk it up as a lesson learned and be thankful that you did not leave your precious child in the hands of irresponsible adults. If they really would do such a thing as deliberately leaving your daughter, would you really want her under their supervision? I certainly wouldn't.
I'm very sorry that your daughter was disappointed. The children should be what it's about anyway.