Well, what would you have done if you owned that aeroplane? I've had to leave mine away from home a couple of times. I collected it, paid anything that was due, and took it home. I'd have done the same if it was a rental. I do think the owner should have contacted you to ask you if you preferred to fetch it or pay for someone else to do it, but flying isn't free, even if in an ideal world it ought to be.
When you left it what arrangement did you make with the owner? Or did you just kinda expect it to get home by itself? Try putting yourself in the owner's place, maybe there was a bit of a communication problem and they weren't happy about the safety of their property?
It's not about safety of the flight, that's a given that you made a necessary diversion. Except that it doesn't end there, you are still responsible for finishing the flight by whatever means, be it yourself or paying for somebody else's time. Time to spare, go by air....