Here's a quick and easy way to determine which of your students has or has not turned in a homework assignment. Assign each student a number. I use the numbers from my gradebook listings. The student is to write that number in the upper righthand corner of every paper that is turned in. Invite a student volunteer to collect the papers and quickly arrange them in numerical order according to the numbers. With one quick look, missing numbers are easily noticed. I can deal appropriately with the student(s) who did not turn in the assignment instead of having to wait until I grade the papers later in the day.