I have a 4 1/2 year old cat, who has just begun using my bathroom rug as his pooping place. It began the night before we left before vacation, we thought it was an isolated incident, but unfortunately it was not. He has been using the rug for the past few weeks almost every night. But he is still using his litter box as well. He is an indoor/outdoor cat and has been spending time both places. He will only use the rug when we are sleeping at night, we do shut the cat out of the bedroom at night, but we have always done this.
If we shut the bathroom door at night he does not poop anywhere else in the house, but we don't want to have to keep the door shut all the time, especially when we have guest, because it is the only bathroom in our house that they have to use.
I am open to any suggestions, thank you for all of your help.

But there may not be anything wrong medically with the animal. The first time he pooped in the rug may have been an accident. But once the smell is in the rug, the cat will do it over and over again. Even a thorough washing of the rug may not eliminate the smell completely.

My suggestion: throw out the rug (I hope it's not a costly one) and get a new rug, an inexpensive one to see what happens. That may solve the problem.

Cat was/is sending you a message - "Up yours" basically lol.

I had to laugh at another post questioning whether a cat would poop in an inappropriate spot deliberately? Answer: absolutely!