I've had a privilege to meet @cass in Oslo, and I can vouch he is a really good person. Rarely do I see someone considerate of other people in his network, and willing to help.

Unfortunately, sometimes, less conscious people will take advantage of that (the takers).

Speaking from experience, the best thing to do is to write-off the loss, write-off the person that wronged you, and move on asap. Not doing so will only cause further losses in time, energy and well being.

Thank you for bringing the issue up, and helping others avoid falling into the same trap.