By no means do I want to bust anyones bubble but this is just to help you out next week.
If you are doing an EXTREME calories deficit, it is totally possible, I had to buckle down a week before a wedding once and lost 5.5 pounds in a week, but this was truly extreme and my exercise regimine was pushed to the max.
Now...even if you didnt do that, even if you stuck with your normal plan but increased your exercise a little, Im sure you lost 3, maybe even 4 pounds; and maybe your water weight is working in your favor this week. Once again, the ONLY reason I wanted to chime in is to tell you to not get frustrated if you see a little bit of a gain next week.
Nonetheless....you are doing AWESOME...kudos to you on any loss.