What? A 3500 or more deficit of the week and gained?

escapeartist90210

So I slipped up a couple of days ago and went over like 200 calories above maintenance but since I do ESE, I eat very little or nothing the next day. I made at least 3500 deficit or more but gained 3 pounds outta nowhere? I mean, usually I'm good with this stuff but I'm confused as to why? Water weight maybe? It can't be muscle considering it takes months to put on muscle and I haven't been lifting as of late. Gained about 3lbs.