My rear o2 sensor has no nuts

So i went a did an oil change and when i got done and drove over to recycle the old oil and i started to hear a nasty rattling sound. I thought it was going to be the rear skid plate and after i removed it again (i took it off to do oil change) i thought i would grease up all the spots couldnt been happier they were all in perfect allignment and easy to get to.
As i shimmied to the rear of the truck i noticed a small shield hanging funny and low and behold there were no nuts holding it on. long story short what a pain to replace. F.... it im gonna pay someone to change my oil from now on Ha ha ha. i am supprised it didnt throw a code

 

when i took my truck in to get my new muffler welded on, the guys came out and said the same of my rear o2 - i asked to see it, sure enough, no nuts, no heat shield. They had a couple new laying around and slapped 'em on for free.