So sorry to hear that you got fired, but more upset that some asshole in your company found them. Most people will not post your photos for fear of losing their job too. Especially those in charge at your corporate office. So, you can breath easier about this. (and if you find them online, then get a good lawyer and make a case because you have already been punished by the loss of your job with the company) What pisses me off the most, is that these are your photos and not like you were surfing the web at work on their time.
Moving forward. Most companies that make USB stick/disk/flash drives, companies like: Sandisk. Now provide a built in LOCK on their product so you can password lock what you do not want others to see. My only other comment is that even though this cost you your job, at least you know where they ended up and not worried about who really has them now. Also, most people have taken pics of their wife in the nude, etc.. This is not like something unusual or weird that you have done.
Finally, at least you think your wife is hot / beautiful enough to want to take photos of her. Many men can't say that about their wife. Take heart in this and good luck on your next job.
http://www.sandisk.com/products/usb/drives/