CSV file last 6 digits changed to zero in a 12 digit number

I have scoured the internet for a solution to this problem and apparently it's not a common problem.
I work for an internet wholesaler and we receive product orders that contain UPC codes in CSV format. The UPC codes are 12 digits, not 15+.
When I open the file the UPC's are in scientific notation, as expected, which is not a problem at all. The problem is that the last 6 digits are zeros. While still in scientific notation, I can look in the formula bar and see the 12 digits and the last 6 are zeros before I even touch it. No kind of formatting gets the correct data back.
I'm suspecting perhaps it's on the creating end of the file, but a co-worker is supposedly opening the same files without this problem. I don't even know which end to start on. I'm hoping someone here may be experienced enough to recognize this weird behavior. Thank you to anyone who may be able to help at all.

I tried to upload it, but got invalid file message. I have several files like this and I tried each one. I can open them in excel or even notepad, so I don't know what the deal is with them. But I do thank you for your time.

The file is 1.3 kb. It is an excel csv file. Yes, I'm using the 'go advanced', etc to attempt the upload. When I start browsing for my file it doesn't even show in the selection window. So I typed the name, it started autofiling as tho it is there but not visible, and then errors as an invalid file.It shows up in any other application that I use to browse all files - excel, notepad, even in paint. And it opens in any program that opens csv. I even emailed it from work to home, no problems. Weird.

lol, I"m grasping at straws too. Yes that's correct that I can't see it, and I do indeed have it set to all files.

Yes, I'm looking in the folder where I saved it. While taking some screen shots to show you this, I moved it to another folder with fewer files, so it would be easier to see and I discovered that when I use the upload utility on this site, I can see only one of the files in the folder. The folder it is in now also has a text document, a cad file, a jpeg. Out of the four, the only file that shows is the jpg.
Using the insert image option on this reply form, with 'from computer' checked, I've attached a screenshot of the files in the folder on my pc, and a screenshot of what shows in the upload utility on this site.

newfolder7 files.jpg

IE 9 - update version 9.0.10

Well that answers that question.
But I did follow instructions. Martin said zip it. I zipped it. If I had been told to make a .zip I would have made a .zip
It never ocurred to me that the list of permissible files on an excel site would be so narrow.
Especially since I've used all those file types in conjunction with excel on a regular basis for years.
Yes, I can attach as it to an email. I emailed it to myself at home.
Thanks for all who've tried.

I have already tried importing it and setting the format to text in the wizard. I've tried every kind of format, and every formula that I can think of. So has my supervisor at work. I would say it was done by the person who sends them to us except that a co-worker opens the same files in excel with no problems and no spoiled data.

Indeed, and resaving it compromises the whole deal, so might as well mark this thread closed. I thank you for your time.

martindwilson's list of allowed file formats suggests that .txt is an allowed file attachment. Since a csv file is a "special" type of text file, rename the csv file to have the .txt extension and see if that will upload to the forum. Anyone who wants to debug it as a .csv file can then rename it back to .csv.

Along the same lines, have you tried opening the .csv file in a text editor (like Notepad or Wordpad) to see what the text file looks like without Excel's "interpretations"?