I find it so interesting that English really focuses on intent. So many words mean that something was done purposely, like 'lying' and 'stealing', and they are common words. Although we do have the word 'misspeak' to convey saying something that is not true without the intent of deceiving, I bet that more people know what lying is than misspeaking.
I can't even think of a single word that really conveys the idea of taking something without permission without the intent to do so, but such things are not uncommon (think of how many pens or pencils you acquired or lost in school due to exactly that). There is the tongue-in-cheek phrase "borrowing without asking", but it's a phrase and not really sincere.
People often ignore the intent in their words. This is lesson number one when it comes to careful and effective writing. Make sure that if something happens on purpose, you use the word for it, and if it is accidental, you explain that. Otherwise, you can get into a whole heap of unpleasantness.