How did you grow your phage? Try longer culture time and richer media if you want more phage. Besides, you might still have enough phage even if you can't see them. In my experience, precipitated phage doesn't form a pellet on the bottom as cell pellets. Instead, they form a tiny streak along the wall of the tube and can be difficult to see.

Just use a small volume of buffer to wash the inside wall of the centrifuge tube afterwards, take a small portion from the suspension and run it on SDS-PAGE. You may still see it. If you have an antibody, western blotting would be very sensitive to detect very low amount of phage. Also, do a phage titer experiment with the resuspended phage solution to make sure that you have phage and determine the actual yield.

Thanks dear Wei