[joeysteele]

From what you say in your posts,you should be okay, he should have asked you if the ladders could have been put somewhere safe until he got back for them.

If he left the ladders outside, then it is his bad luck someone grabbed them.
You allowed him to leave his tools, then his ladders again after getting his tools, you have done more than you needed to, you could have insisted on all being removed the day he was stopped from doing any more work.
You accommodated him, it is his fault for not securing things, I guess he would be expected to put this down to experience.

Good luck.