That is a terrible ruling.
I'd accuse you of the angle shoot but you asked the dealer and it was him who called the floor.You say yourself it was clearly meant to be 3k therefore the bet is 3k. All it takes is a quick "that's 3k not 300 yeah?" from the dealer and the issue is sorted. Spirit of the game and all that.
FWIW, I asked how much because there was a single chip and I didn't hear clearly what the guy said.
I'm smart enough when I want to shoot an angle not to start a thread on blonde about it.
There is a responsibility on the player to make it clear how much they are betting. If you don't have correct change, make sure the dealer knows what proportion of the bigger chip is going in. It can be a way of disguising nerves if you only say a single syllable, rather than having to say the exact amount. On reflection, that might be why my villain said "three" confidently when "three thousand" might have given away a croak or a tightening of the larynx.
I think the majority of the comments in my linked thread were in jest but I don't mind defending myself if there is an issue. As it was, as you say, I didn't call the floor and, if the dealer had asked the villain for clarification (which, let's be honest, is the common sense thing to do), I would have been absolutely fine with the outcome.
Game of cards.