Do I have a right to be upset now?

My husband and I have another couple that we have just started hanging out with this past year. They are great and we all get along so well and have a great time. We have been having a hard time lately making plans due to them getting married and us not having a sitter. We always take what we can get, if only a lunch date. So this past month, we made plans for them to come over this weekend for the night. We even finalized them last week. Well this morning they called and said they had totally forgotten about our plans and made a promise yesterday to someone else for our upcoming weekend! Even though I played it cool to them, I am totally offended. They made plans with us first, so they should have spoken up and told the other people that they were unavailable! I am even more offended that they so easily forgot......I have been stoked since we made the plans. Do I have a right to be mad??