Purchase made that I didn’t make?

I logged on to steam today, and my steam wallet was empty. I checked my purchase history, and their was a DOTA item worth 3 cents that ‘I purchased’ for my whole balance.

I definitely didn’t make this purchase, leading me to believe my account is compromised (I changed my password in response).

I checked Steam Support, and none of the options really pertain to this issue.

Does anyone have any suggestions on what I should do? It wasn’t a massive amount of money, but losing 15 dollars for nothing doesn’t feel great.