But I'm not sure that it also means the Cavs "lost" it. Are you?
You're awfully fond of asking me whether I'm "sure" of things. The answer is always No.
That said, I don't think it's a very good trade for Cleveland, but that's because I don't think much of McInnis. He had one decent season with the Clippers but other than that is a journeyman scrub. Cleveland saves a few dollars this year, but they're stuck with McInnis for next year -- they could have let Miles walk this summer -- so it's not even a very good deal for them financially. And in terms of talent, one suspects that they could have gotten a better offer for Miles from another team.
And in response to your next question, no, I'm not sure that they didn't try.
However, I do agree with your basic sentiment that Miles is unlikely to amount for much. I frankly never thought much of him in the first place, but that's because I'm not all that big on "potential" as a way for evaluating a player's value.