It's a gray area actually. You didn't ask for money to take them out (except for gas which is legit, I can't see any court actually convicting anyone for sharing gas expenses). I would try again and return the money. I can see the gesture, but in long run it's like paying or tipping you for your services (which would be guiding).

But, usually for myself, we normally do a "I pay for gas, you pay for breakfast" thing. This way, no confusion there. I guess if they wanted to, they could say there was a payment offered. But breakfast? Come on. But could see a lawyer saying so. But you did the right thing by attempting to contact them. If anything, give the money to the friend you were helping out. That way, they can carry the burden if it bothers you that much. As much as I hate to say it, you've exhausted all you can do. Just take it as appreciation and BUY MORE GEAR!!!! lol. Hate to make it sound smartalec, but not much else you can do unless you donate it to charity.