Ok, here's the thing:
Same thing happened to me not long ago (about 2 and a half weeks). After my bank saw the fraudulent charge, they froze my account. I thought the same thing "this was the only time my card got used in the last month. Must be on their end."
I called tree stuff and told them that my card got compromised and that they were the only ones to handle my card for the last month.
They sprung in to action immediately. Luke called me, asked for more details, then contacted their IT guys. They in turn contacted me and asked even more questions. Turns out that the way the fraudulent charges where done, there was no way (like physically no way) for the info potentially stolen from them to be used as quickly as it was.
In other words, the leak was on my end. It was probably either a) due to one of the many major corporate leaks that has happened recently or b) due to spy/mal ware on my phone.....more likely one of the corporate leaks, though.
IOW, the folks over at treestuff got on the ball triple quick. They used all the resources they had to quickly see if they had been compromised. They took a personal interest in the matter.
I too will probably start calling in my orders, but it's because I don't trust the transmission from my phone, not their ability to guard the info on their end of the transaction. When I am ready to order, I'll write down parts numbers or I'll ask to speak with either Luke or Nick. They know the gear, and would be willing to take a description instead of a part number.
Bottom line: I'll continue to do business with them unless there emerges a vendor that does a better job, but that in itself is a tall order as they don't have many areas they can improve in, and those few areas are being addressed as quickly as they can be.