Okay I was down to 135 and Saturday night I didn't get much sleep (not to mention getting to bed really late), and on Sunday morning I weighed 137. I also didn't eat my 1200 calories like I was supposed to on Saturday, so I wondered if the 2 pounds was from that. But on Sunday I ate 1222 cals and Sunday night slept for almost ten hours. This morning I'm back to 135. Weird I know, but I think it might be a combo of the cals and sleep. Maybe I'll make sure to get at least 8 hours from now on.
The 2 pound difference you experienced could have been a result of many things - water retention, the foods you ate (or didn't eat), etc. but the lack of sleep would have confused your metabolism as well.