Lookup & Reference function

I am consolidating a project schedule based on a more detail schedule and I am having trouble finding a formula to do the following:

I have a column of data that has either a number (project number) or it has zero in it. In a different worksheet, I am trying to create a formula (function) that will look a this column of numbers, find the one cell in the column that has a project number and then put that project number in this cell. I have looked at a lot of the lookup and reference functions, but can't seem to find any that work.

I was using a nested IF statement, but I have too many rows in this column becuase I got an error that there is too many arguements.
Any suggestions would be appreciated, it's driving me crazy that I can't figure this out.

If you only have one number can't you just sum the column?

=SUM(A:A)

Or have I misunderstood?