This sounds like a stupid question but, after uploading a file the file isnt in the location php said it would be.
First the simple test page:
The temporary file is deleted when the PHP script that received it has finished running : it is just a temporary file.
The PHP script to which you are posting the form -- upload.php -- should move the temporary file to a non-temporary location, using move_uploaded_file()
Basically, the idea is :
If the upload doesn't finish successfully, or if you don't move the file somewhere else, the temporary file is automatically deleted.
As a reference, you should read the following section of the manual : Handling file uploads - POST method uploads
Quoting the part of it which is related to your problem :
The file will be deleted from the temporary directory at the end of the request if it has not been moved away or renamed.