It is not easy to find one managerial behavior that can illustrate several of the most glaring forms of managerial incompetence, but your manager has managed to do so. His antics in this situation point to a complete failure in terms of communication, focus, follow-up, feedback, planning, organizing, and empathy, just to name a few deficiencies.
To make matters even worse, he also trashes the entire issue of respect for an employee. Not only did he set your assignment aside, he set you aside, all without a word of explanation.
Importantly, the problem in this situation is not that your manager no longer needed your project. Any number of internal or external forces can cause this to occur. The problem is that your manager totally ignored you.
In terms of near-term strategies, you should meet with him on a regular basis on every project he assigns to you. Let him see the progress that you are making, and ask for his suggestions and feedback.
If you find other instances in which he basically views you as being invisible, perhaps that is exactly what you should become. There are plenty of work situations, perhaps even in your company, where employees who work long hours to meet deadlines are actually valued.
| 
