Amber, we'll never know. Everything is possible.
There is a possibility that your client had ulterior motives and there is also a possibility that he was genuine and perhaps the other girl had signed an NDA, or didn't want to admit anything for discretion or not to expose herself. Or maybe he lied about her to either make you jealous or to convince you that he has done that before. He spent quite a bit of money on you but I assume he got his money worth in sex so it is not like he lost even if he has dodgy incentives that didn't come to fruition.
You did everything right. You sought advice, you probed your client and took a decision with your mind and gut feeling. The way I see it is like any business, you had to invest something important (your time and safety), you evaluated the risk and came to the decision that this was unacceptably high for whatever the reward was. And you have even met your client a couple of times, whereas we had very limited information here.
I am not perfectly sure whether this is worthy of a warning, but it looks like he did lie to you about the other girl and seemed too good to be true with everything else so best safe than sorry imo! It might be good to post something for caution if others agree.