Send him an envelope back with a hand made receipt of what you spent on that cab and bus fare. The note attached can be whatever you want but you can just say "You now owe me [insert amount here] for costing me time and money with your trolling. I'll be taking my payment from you when you least expect it. Have a great day." - or doing nothing works too if you don't want to "start" something with your ex.

i guarantee even after this post you'll still get comments saying 'what a dick, you're better off without him'. it's good that you're still able to be civil but it was still harsh for him not to help you out when it's serious