Why is it called a דבר שאינו מתכיון. Since twice in Gemara Shabbos Rashi understanding and explaining to us what forgetting is when one leaves a rock on top of a barrel says this first on Shabbos 125b uses the word מתכיון then on Shabbos 142b he uses the word מדעת. So seemingly the words are the same, so why did Chazal find it fit to use דבר שאינו מתכיון and not דבר שאינו מדעת?
The term מתכוין refers to intention. מדעת means awareness.
There are times when the main point is one's awareness of an action, not one's intent. For example, we find in the gemara the concept of אבידה מדעת where something is considered to be "lost" with awareness.
Example: putting items in a garbage pile which will be emptied (Baba Metzia 25b).
It's not a question of whether or not I "intend" on the items being permanently lost; it's a question of whether I was aware that I was putting the items in a place where I might not be able to get them back.
Regarding Shabbos, the main issue is my intention- what I am intending to do? If I'm not intending on doing something, the fact that I know it might happen will be irrelevant.
(The exception to this is פסיק רישא, a type of action where the result is so definite and clear that we say that your knowledge of the action is the equivalent to having intent. See Shabbos 133a)