Passport backs up all the data and LOSES IT ALL when you disconnect from the computer

I have WD My Passport.  P/N WDBABW0010 BSL-02.  Not sure if that is the number you need…Anyway, I thought if you disconnected it from your computer (I have an Imac) desktop, then your data would be there on the Passport.  I made sure it was all ON the Passport BEFORE  I disconnected it from the computer.  When I plugged it back into the computer to make sure the data was there…it had all areas had gone to zero and ther was nothing on it.  A week ago I did an update on the passport, but now this is happening.  I NEED THE DATA TO STAY on the Passport as I need to take the iMac in and get the Yosemite update…Any info on what could be going on here?  Thanks.

Hi questioning_1, welcome to the WD Community. What format are you using for the Passport? NTFS, HFS+, etc? If you click on get info for the Passport do you see the full capacity available? 

I see Capacity available: 954.74.  I had shown a screen shot showing the categories and how much was used to Best Buy Geeks Squad and they said all was well…I had been willing to buy another, if need be.

Under Format it says: Mac OS Extended (Journaled)

Anyone else?

Hi again, I would try running a Disk Utility test and also connecting the Passport to another Mac to verify if the problem happens again, if it does contact support to see if it needs to be replaced. 

How to test a drive for defects or problems on a Mac

I won’t be able to delve into the answer completely for a few days.  However, when I do I will be back to either tell you it is resolved or ask for further help…Thanks for your help so far, though.

I did run the disk utility and there WAS an item to repair.  I repaired it and then took the device to Best Buy.  A Geek Squad guy hooked it to a Mac and my data was there.  However, he recommended just holding on to this device in case of a worst case scenario and buying a new device.  So that is what I did.  At least I will have two backups on hand if the worst ever happens…

I thank you VERY much for your advice and teaching me how to look for a problem in the device and how to repair it.

Thanks so much!  

Thanks again!