If I had bid for a record and the auction was closed early without warning I would have been a bit pissed. Who wouldn't?
I would not have done what you did though. Like I said, I would have sold my copy and let the other run.
And anyway, I already have the 45 mate, not that it makes the least bit of difference.
You can do what you want, like you say it is your tune.
That said, it might be nice to let people know what your rules are and that they are likely to change at whim.