Is it plagiarism if I copy somebody else's answer I already solved but misplaced? For an assignment, I was supposed to do some tedious calculations and essentially compute a certain number of things and then just list them as answers, one after another, without the calculations. There were about 15 of these things that I had to list.

I did this, and then misplaced the paper on which I had written them. I was sitting in class getting ready to hand in my paper when I realized this. It was the last paper in the stack and I guess it just got lost somewhere. 

So what I did was that I found the solution online, and then just listed those things down again and turned it in. The problem is made worse by the fact that I listed the 15 things down in the same order as the solution found online. There wasn't a "natural" order to the things, apart from maybe the first and last thing, and therefore, there were 13! = 6227020800 different ways of listing them, and so of course it will look very suspicious if somebody noticed that I just happened to have the same order as this other solution.

Is this plagiarism? What should I do if this is caught? I am considering writing a mail to my instructor right now, but I could also leave it be and hope it is not caught.



EDIT:

One of the answers below raised another question. What if my original solution was wrong? In this case, I definitely cheated by copying from the correct solution, but, since I did not know whether my original solution was wrong, I did not cheat intentionally, so .... ?
Is it plagiarism if I copy somebody else's answer...


Yes. Without even reading anything else you wrote. This is exactly what the word "plagiarism" means.