I think my cat is stuck or hiding somewhere in the ceiling of my basement.Help?

He's not meowing or making any noise. In our boiler room there are openings to where he always goes and hides..but he usually comes back. And in the past couple of days he's been sick and he's not eating much. He did the same thing yesterday and I was looking all over for him but he eventually came out. This morning I came to check up on him and he wasn't there. And my mom checked on him in the afternoon twice and he wasn't there. When I came back from school i stayed in his room for a couple of hours and he didn't come out. I can't find him! Please help?