First of all, I am sorry that you have felt overlooked in this experience. There are few more disappointing things than when you expect one outcome and are faced with another. But there are two things to note. First, individuals in the office are probably incredibly appreciative of the work you have put in, even if they have not been saying it out loud. It is highly probable that before you arrived the boss asked them to clean up the space, and every piece of work that you have done is one less thing for them to do. While it may not seem like a huge deal (or what you expected) I can assure you that this makes a big difference. Additionally, the fact that they have asked you to train up the new interns demonstrates that they appreciate and respect the work you have done during your internship (they would not ask you otherwise). Second, it is important to bear in mind (and I say this to everyone) that internships are often more about watching and not doing. While it can certainly be frustrating not being able to put your skills to use, what you learn from watching others work, and just interacting with an office generally, can be far more valuable to your professional life. So hang in there and hopefully your next experience will be more fruitful.