I often find that lending out materials is never a good thing. One of the tricks I do is keep "disposable" materials that I can give away and not freak out when I loose them. I used to carry a small set of three throwing knives, I never threw them in my life, but I did lend them out for eating when I would go camping.
Often in situations like that you learn how unprepared people are for small SNAFU's like that.
It sounds like you had a successful venture while you did loose some materials; you learned a lot of lessons and probably taught a lot of people. Now I have to go lookup this flashlight you talked about lighting up the store like the sun..