If you delete a file and create a new one, then on some filesystems the inode number is re-used. That will prevent the file input from seeing it as a new file. For example
echo foo > foo ; ls -li foo ; rm foo
echo foo > foo ; ls -li foo ; rm foo
gets me
4272123 -rw-r--r--. 1 user user 4 Feb 13 11:41 foo
4272123 -rw-r--r--. 1 user user 4 Feb 13 11:41 foo
It re-uses inode 4272123. Ugh!